Copyright © 2010 by the author(s). Published here under license by the Resilience Alliance.
Esselman, P. C., and J. J. Opperman. 2010. Overcoming information limitations for the prescription of an
environmental flow regime for a Central American river. Ecology and Society 15(1): 6. [online] URL: http://
www.ecologyandsociety.org/vol15/iss1/art6/
Research
Overcoming Information Limitations for the Prescription of an
Environmental Flow Regime for a Central American River
Peter C. Esselman 1 and Jeffrey J. Opperman 2
ABSTRACT. Hydropower dam construction is expanding rapidly in Central America because of the
increasing demand for electricity. Although hydropower can provide a low-carbon source of energy, dams
can also degrade socially valued riverine and riparian ecosystems and the services they provide. Such
degradation can be partially mitigated by the release of environmental flows below dams. However,
environmental flows have been applied infrequently to dams in Central America, partly because of the lack
of information on the ecological, social, and economic aspects of rivers. This paper presents a case study
of how resource and information limitations were addressed in the development of environmental flow
recommendations for the Patuca River in Honduras below a proposed hydroelectric dam. To develop flow
recommendations, we applied a multistep process that included hydrological analysis and modeling, the
collection of traditional ecological knowledge (TEK) during field trips, expert consultation, and
environmental flow workshops for scientists, water managers, and community members. The final
environmental flow recommendation specifies flow ranges for different components of river hydrology,
including low flows for each month, high-flow pulses, and floods, in dry, normal, and wet years. The TEK
collected from local and indigenous riverine communities was particularly important for forming hypotheses
about flow-dependent ecological and social factors that may be vulnerable to disruption from dam-modified
river flows. We show that our recommended environmental flows would have a minimal impact on the
dam’s potential to generate electricity. In light of rapid hydropower development in Central America, we
suggest that environmental flows are important at the local scale, but that an integrated landscape perspective
is ultimately needed to pursue hydropower development in a manner that is as ecologically sustainable as
possible.
Key Words: dams; environmental flows; fish assemblage; Honduras; hydrology; traditional ecological
knowledge; tropics
INTRODUCTION
Construction of dams for power generation is
expanding rapidly in Central America because of
high population growth, rural electrification efforts,
and increased demand for electricity (Scatena
2004). Electricity consumption throughout the
region is increasing 5%–9% each year (Comisión
Económica para América Latina y el Caribe
(CEPAL) 2006). Hydropower is a preferred
generation method in Central America because the
primary resources, water and topographical
gradient, are in high supply and because it is a
proven solution to national energy needs—
approximately 50% of the electricity in Central
America was generated by hydropower dams in
1
2005 (Energy Information Administration (EIA)
2010). Costa Rica alone built more than 30 new
hydroelectric plants during the 1990s (Braga et al.
2000, Anderson et al. 2006). A recent assessment
of future hydroelectric development anticipates an
expansion in hydropower capacity in Central
America, with 370 planned hydropower dam sites
with a potential aggregate installed capacity of 16
165 MW (Burgués-Arrea 2005).
Because dams can cause substantial social and
environmental impacts (World Commission on
Dams 2000), proposed hydropower expansion on
the scale contemplated in Central America raises
important questions about sustainability. Although
much attention has focused on the human
Department of Fisheries and Wildlife, Michigan State University, 2The Nature Conservancy
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communities and habitats displaced by reservoirs,
dams can also significantly affect downstream
habitats and livelihoods by altering a river system’s
natural flow, sediment, and energy regimes (Baron
et al. 2002, Postel and Richter 2003, Fitzhugh and
Richter 2004). River flow can be considered a
“master variable” that controls many of the
fundamental physical, energetic, and biological
characteristics of a river system and its floodplain
(Poff et al. 1997). Disruption of the natural flow
regime can therefore disrupt entire river ecosystems
and the socioeconomic activities that depend on
them (Sparks 1995, Walker et al. 1995, Poff et al.
1997, Baron et al. 2002, Postel and Richter 2003).
In part because of altered natural flow regimes,
species in freshwater ecosystems are endangered at
rates far higher than those in terrestrial and marine
ecosystems (Richter et al. 1997, Ricciardi and
Rasmussen 1999). Dam-induced alterations to river
flow can also degrade or change many of the benefits
that humans derive from these ecosystems. This is
particularly true in developing countries where
millions of people rely directly on flow-influenced
ecosystems—rivers, floodplain forests, riparian
wetlands, and nearshore marine ecosystems—for
their basic subsistence needs (Postel and Richter
2003).
In Central America, budgets are small or nonexistent for physical or biological data collection,
and comparatively few scientists are available to
conduct in-country research (Pringle et al. 2000).
As a result, data available for developing
environmental flow recommendations are scarce or
completely lacking for most rivers, and financial
constraints greatly limit research and modeling
efforts. Thus, developing environmental flow
recommendations for the region’s rivers will require
technically defensible methods that do not rely
heavily on empirical data. Richter et al. (2006)
described a process—now referred to as the
“Savannah Process” for the river in which it was
first applied—in which environmental flow
recommendations can be developed in an
interdisciplinary workshop setting with expert
input. This approach integrates whatever
information is available, along with expert
judgment into a framework that can be adapted to
the level of information and funding available. In
this paper, we present a case study of how we
adapted the Savannah Process to develop
environmental flow recommendations for a Central
American river, the Patuca River in Honduras, for
which little scientific data and few experts were
available.
Although many definitions of sustainability have
been offered, most efforts to describe sustainable
hydropower emphasize that hydropower benefits
should be balanced with the ecological and social
values of a river system, and that environmental and
social impacts must be avoided, minimized, or
mitigated at all stages of the development process
(International Hydropower Association 2006).
Because most riverine resources and values depend
on the flow regime, this suggests that sustainable
hydropower must strive to protect the aspects of a
river’s flow that are important to society and
ecosystems (Bratrich et al. 2004). Such flows—
often called “environmental flows”—have been the
focus of much research around the world. The vast
majority of environmental flow projects and studies
have been conducted in North America, Europe, and
Australia, countries with relatively high levels of
financial resources and relevant scientific and other
expertise. Fewer efforts have been made to develop
environmental flow recommendations for countries
in the developing world (Tharme 2003), where
information and logistical challenges commonly
differ from those in economically well-developed
countries.
The Patuca River encapsulates many of the
logistical, environmental, and social challenges of
developing environmental flow recommendations
in Central America. The Patuca is the third longest
river in Central America and supports important
aquatic biodiversity and an array of estuarine and
nearshore ecosystems. The Honduran government
has approved the development of a hydroelectric
dam, known as Patuca 3, for the currently
unregulated river. Below the proposed dam, the
Patuca River flows through three national protected
areas that include the roadless territory of two
indigenous groups, the Miskito and the Tawahka,
who number approximately 6400 and 1100 people,
respectively, in the watershed (Fig. 1) (McSweeney
2002). Typical of many other communities with
subsistence-based livelihoods, the Miskito and
Tawahka villages of the Patuca River are dependent
on riverine and riparian ecosystems for navigation,
agriculture, artisanal fisheries, bush meat, edible
and useful plants, and drinking water (McSweeney
2002, 2004).
As is the case for most rivers in Central America,
ecological data are largely unavailable for the
Patuca River. As a result, we drew heavily on
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Fig. 1. The Patuca River and its location in the country of Honduras in Central America. The study
reach stretched from just below the dam site near Nueva Palestina to the village of Kuhrpa in the coastal
plain. The hydrological gauging site at Cayetano mentioned in the text was located just below the dam
site, whereas the one at Kuhrpa was located at the village with the same name.
traditional ecological knowledge (TEK; “all types
of knowledge about the environment derived from
experience and traditions of a particular group of
people” (Usher 2000)) and expert understanding of
basic riverine processes as primary information
sources to aid the development of environmental
flow recommendations for the river. Traditional
ecological knowledge has been used frequently in
other contexts to inform policy and natural resource
management decisions and to incorporate the
concerns of local communities (e.g., Klubnikin et
al. 2000, Ellis 2005). An abundance of research has
reinforced the idea that local and traditional factbased claims can be scientifically accurate. For
example, previous works comparing traditional
knowledge to empirical scientific studies have
shown that fishermen can recognize taxa, can have
accurate knowledge on both fish behavioral traits
(Morrill 1967, Johannes 1978, 1981) and
spatiotemporal changes in fish assemblage
composition across seasons (Poizat and Baran
1997), and can accurately attribute causation to
complex limnological occurrences (Calheiros et al.
2000). These studies demonstrate that, when
collected carefully, TEK has the potential to be a
highly accurate source of information.
Below, we present the process used to incorporate
TEK and expert knowledge into an environmental
flow prescription for the Patuca River. The goal of
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this environmental flow recommendation was to
define the suite of flow conditions that must be
maintained to preserve important flow-dependent
ecological and social characteristics of the Patuca
River. After describing the methods used, we
present our findings and flow recommendation, and
discuss how this project informs the debate over
sustainable hydropower.
BACKGROUND AND SITE DESCRIPTION
The Empresa Nacional de Energía Eléctrica (ENEE)
is the quasi-governmental organization responsible
for electric energy generation and delivery in
Honduras that is overseeing the planning and design
of Patuca 3. In 2006, ENEE entered into a
Memorandum of Understanding (MOU) with The
Nature Conservancy (TNC) to facilitate the
development of environmental flow recommendations
by ENEE for the design and operation of the planned
dam on the Patuca River (Patuca 3). The role of TNC
was to provide ENEE with essential exposure to
practices and approaches relevant to ecologically
sustainable water management. Both parties agreed
that the end-product would be an environmental
flow recommendation that would inform Patuca 3’s
environmental impact assessment. The MOU also
stated that TNC’s participation did not imply an
endorsement of the dam and that the final flow
recommendation would be ENEE’s product
exclusively.
The Patuca River begins at the confluence of the
Guayape and Guayambre Rivers, and flows 465 km
to the Caribbean Sea, with a drainage area of
approximately 24 000 km2 (Fig. 1). Approximately
one-third of the basin has been deforested for cattle
pasture, agriculture, and urban development,
primarily in the headwaters above the proposed dam
site. The low-elevation portions of the watershed
are heavily forested and roadless except for the area
very close to the coast, which has limited road
access. The river flows through three large protected
areas: Patuca National Park, the Tawahka-Asangni
Biosphere Reserve, and the Rio Platano Biosphere
Reserve (Fig. 1). The latter two protected areas were
created in recognition of their unique cultural and
biological diversity. Along with the contiguous
forests on the Atlantic coast of Nicaragua, this
region encompasses one of the largest roadless areas
in Mesoamerica.
Precipitation in the Patuca basin is highly variable,
both temporally and spatially. The basin is subject
to an annual dry season between January and May,
with most of the yearly precipitation occurring
during the wet season from June to December. The
low-elevation coastal plain receives nearly 3000
mm of rain a year, but because the Honduran Central
Highlands are situated between the Caribbean and
the upper watershed and block frontal storms, the
steep headwaters (more than 2000 m above sea
level) receive only 900 mm of rain a year. The
seasonality of rainfall leads to a corresponding
seasonality in river discharge (Fig. 2). The
hydrology of the Patuca River also displays
considerable between-year variability, with
individual years that range from very dry to very
wet (Fig. 2). The area also occasionally experiences
severe storm events, such as when Hurricane Mitch
deposited up to 1.8 m of rain in some locations in
October 1998 and caused the middle reaches of the
Patuca to rise 14 m within a few days (DeVries
2000). The floods associated with Mitch were
among the most extreme on record anywhere in the
world (Smith et al. 2002), and had a strong influence
on the Patuca ecosystem and the human
communities that depend upon it (McSweeney
2002).
The Patuca is a large river by Central American
standards, with an average instantaneous yearly
discharge of 135 cubic meters per second m3/s at
Cayetano near the dam site, and 429 m3/s at Kuhrpa
downstream (Fig. 1). Mean monthly discharges are
as great as 232 m3/s and 683 m3/s, respectively, at
these locations in October. The river below the dam
site flows through a tightly constrained valley with
little floodplain until it reaches the confluence with
Rio Wampu. In the valley, the river channel
alternates between heavily boulder-strewn rapids
and long trench pools. Below Rio Wampu, the river
enters the coastal plain and flows with wide
meanders across an extensive floodplain, exposing
large sand bars during the dry season.
Nine communities—three indigenous Miskito, five
indigenous Tawahka, and one Mestizo—are located
along the banks of the river between Kuhrpa and
Nueva Palestina (Fig. 1). Approximately 300
Mestizo settlers also live in squatter homesteads
along the river within Patuca National Park. The
indigenous communities on the middle Patuca
subsist on agroforestry and slash-and-burn
agriculture supplemented by animal husbandry,
fishing, hunting, and foraging. Agriculture is
concentrated on the active flood plain, and the river
is an important source of water for cooking and
bathing, with drinking water coming from
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Fig. 2. Representative dry-, normal-, and wet-year hydrographs for the Patuca River at Cayetano,
showing the stable low-flow conditions of dry season (January to May), and higher base flow and more
variable hydrological conditions of the wet season (June to December). Q = discharge measured in cubic
meters per second.
tributaries. Communities along the waterway
depend heavily on the river for transportation,
particularly for trade of cash crops (rice, cacao),
gold, livestock, and forest products (McSweeney
2004). Transportation is accomplished using dugout
canoes, locally known as “pipantes,” carved from
large rainforest trees. Commercial pipantes are
equipped with 40 or 60 hp outboard boat engines.
The main upstream trading destination is Nueva
Palestina, which, although a longer trip than the
downstream trading center of Wampusirpe, is
economically more beneficial because products are
cheaper when purchased there.
of the entire Patuca watershed (12 000 km2) lies
above the dam site. The dam will have a height of
60 m and a width of 208 m at its crest. The reservoir
will flood portions of both the lower Guayambre
and Guayape Rivers, will have a surface area of 72
km2, and a volume of 1.2 billion cubic meters. The
proposed power plant includes two turbines and a
total generator capacity of 104 MW. In the current
design, the turbines are sized for maximum
discharge of 135 m3/s each, and each turbine cannot
operate efficiently below 40 m3/s (Sinotech
Engineering Consultants 2007).
The proposed site of the Patuca 3 hydropower dam
lies 5 km below the confluence of the Guayambre
and Guayape rivers (Fig. 1). In October 2006, ENEE
signed a MOU with Taipower to design and
construct the proposed dam. Taipower hired the
engineering firm Sinotech to complete feasibility
studies and design the project. Approximately half
METHODS
The process to develop environmental flow
recommendations for the Patuca River involved
multiple steps and included hydrological analysis,
field trips to gather TEK, and workshops (Fig. 3).
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Fig. 3. Flow chart showing process used in this study to prescribe an environmental flow regime for the
Patuca River.
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Hydrological Analysis
Field Reconnaissance
To understand how future dam operations will likely
alter the hydrology of the Patuca River, we used the
Indicators of Hydrologic Alteration (IHA) software
to compare the natural flow regime (herein referred
to as the “unregulated” state) to a computersimulated managed flow regime with no
environmental flows (herein referred to as
“regulated”). The IHA software is a hydrological
assessment tool that uses daily flow data to describe
and assess human-induced changes to the natural
flow regime (Richter et al. 1996, Mathews and
Richter 2007). The IHA output describes a river’s
flow regime in terms of environmental flow
components (EFCs), which include low flows
throughout the year, high-flow pulses, and floods.
The EFCs can form the constituents of a
recommended environmental flow regime (Mathews
and Richter 2007). For the IHA analysis, the
unregulated flow data came from an ENEE gauge
near the dam site (Cayetano) with 29 years of daily
flow data, whereas the regulated flow data were
produced from Sinotech’s operations model that
simulated with-dam daily flows for the same
location and time period (1973–2001). Because
only the model results and not the model itself were
available to us, we were unable to conduct
independent quality checks on their estimates.
Corresponding data were also provided for a gauge
near Kuhrpa.
Two field trips were conducted to provide
information about the Patuca ecosystem and human
uses of the river. The first field trip was conducted
in August 2006 (a period of relatively high base
flows) and the second occurred in May 2007 (a
period of low base flows). During the first field trip,
a group of 12 researchers traveled a 250-km stretch
of the middle Patuca by dugout canoe, visiting 11
communities from Agua Caliente (5 km upstream
of Nueva Palestina) to Kuhrpa (Fig. 1). The
researchers used standard questionnaires to conduct
interviews to document communities’ socioeconomic
characteristics, utilitarian and cultural values of the
river, and TEK about the river’s hydrology,
geomorphology, aquatic and riparian fauna, and
ecosystems (see Appendix for questionnaire). The
questionnaires were designed to elucidate factbased knowledge about the river’s flow dynamics;
channel morphology; aquatic community composition;
the diet, habitats, and reproductive details for
important fish species; and value-based knowledge
about aspects of the river and floodplain that have
specific value to communities for economic, social,
or cultural reasons. Key informants in each
community were identified through a process of
peer selection by village leaders. Environmental
engineers collected information about socioeconomic
values of the river, hydrology, and geomorphology;
a soil ecologist and a forester assessed the riparian
ecosystems; and two aquatic ecologists investigated
the aquatic fauna and ecosystem. The assessment of
aquatic community composition from interviews
with fishermen was facilitated by the use of
laminated pictures of species thought to occur in the
area from species lists derived from a preliminary
literature review.
The historical record of daily flow magnitudes
available for Cayetano exhibits a range of variability
from which we defined “dry,” “normal,” and “wet”
year types—a central theme around which the final
flow recommendations were organized (Fig. 2).
Year type was defined by finding the average and
standard deviation of all annual flows for the
available 29 years of data. Dry years were defined
as those lower than one standard deviation below
the average annual flow; wet years were defined as
those greater than one standard deviation above the
average annual flow. This simple approach to
defining year types was used only to characterize
the variability of flow between years. Further
research is necessary to evaluate whether this
definition of year types is of significance to
ecological communities.
The objectives of the second field trip were to: (1)
conduct more interviews to validate information
from the first trip; and (2) gather more information
about how different flow levels affect the villages
along the river. For the second objective,
community leaders were asked to draw bird’s-eye
view maps of characteristic water levels at different
times of year relative to important geographic
features (such as the locations of civic areas, crops,
and fishing grounds), and to comment on the
advantages and disadvantages of given water levels
for their livelihoods. The mapping was always
accomplished by groups of people, most of whom
were men between the ages of 20 and 55 years of
age, and was facilitated by a PhD anthropologist.
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This proved an efficient way of eliciting information
about the relationships between the communities
and the river that fit within the limited time available
for data collection. Data about transportation were
gathered through interviews with boat captains from
villages along the study reach.
Flow Workshops and the Recommended Flow
Regime
Flow workshops were modeled after the Savannah
Process (Richter et al. 2006), in which small
breakout groups focus on the environmental flow
requirements of various components of the river
system. The breakout groups then reconvene and
develop a “unified flow recommendation.” An
initial flow workshop, held in December 2006,
brought together eight environmental engineers, an
agriculture engineer, and a hydrologist from ENEE;
two Honduran conservation professionals from
TNC; seven Honduran experts in aquatic ecology,
hydrology, water quality, and forestry; international
experts in wetlands ecology, hydrology, aquatic
ecosystems, and geomorphology; and seven
individuals from Honduran non-governmental
organizations and government agencies that work
in the Patuca River area. These individuals were
identified by ENEE with recommendations from the
Honduran academic and government community.
The workshop was facilitated by TNC staff
members with experience in applying the Savannah
Process, and workgroups were led by international
experts with experience in developing environmental
flow recommendations. Participants were asked to
focus exclusively on the flow levels and flow
components required to maintain both a healthy
ecosystem and downstream human communities (i.
e., participants were not asked to consider trade-offs
with hydropower production). Workshop participants
drew from three primary sources of information
available in reports and presentations given at the
beginning of the workshop: (1) basic information
on climate, the watershed, hydrology, and technical
information about the proposed dam; (2) the
hydrological analysis comparing unregulated and
regulated (simulated) flow regimes; and (3)
summaries of information collected on the first field
trip, presented in a report that included conceptual
models of the relationships between the flow regime
and fish species with different characteristic lifehistory types (e.g., pair-brooding cichlids,
amphidromous migratory species, catadromous
species, and marine fishes that inhabit freshwater).
Three working groups were formed that focused on:
(1) fish and other aquatic organisms; (2) terrestrial
resources, human communities, and riparian
forests; and (3) channel morphology. Because none
of the participants in the first workshop were experts
on transportation, we addressed this important river
value in a second workshop (see below). Each
working group developed its own set of
hydrological recommendations for the components
of concern. The recommended EFCs were described
in terms of magnitude, timing, duration, and
frequency. Working groups documented their
assumptions about links between the EFC and
riverine processes for each recommendation they
made. Participants also identified the most
important uncertainties and priorities for further
research.
The three groups’ recommendations were
transferred into the Regime Prescription Tool
(HEC-RPT; http://www.hec.usace.army.mil/software/
hec-rpt/). The HEC-RPT allows the visualization of
alternative hydrograph scenarios, and in this case,
was used to overlay the proposed hydrographs of
different workgroups for comparison. Using the
HEC-RPT, we developed a unified recommended
hydrograph that synthesized the three workgroups’
recommended hydrographs, retaining the most
important elements of each.
A second environmental flow assessment workshop
(August 2007) was structured to incorporate
indigenous community members’ knowledge about
the river. Twelve individuals, representing
Tawahka, Miskito, and Mestizo communities—one
or more from each community in the study reach—
attended the workshop. The second workshop was
facilitated by the same TNC staff members as the
first, and breakout groups were led by members of
the field reconnaissance teams that had conducted
field work. Three breakout groups focused on
agriculture, fisheries, and transportation (important
community values identified during the first field
trip). In breakout groups, community members
identified river processes and conditions that either
benefited or created difficulties for their livelihoods.
Several methods were used during the second
workshop to facilitate the discussion about flow
levels. First, we projected photos of well-known
river locations, and community members annotated
the photos to show water heights associated with
important river conditions (Fig. 4). We also used
hand-drawn maps to show how different flood
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levels affected crops and communities (similar to
the technique used on the second field trip). Finally,
the transportation group drew a map of the river and
identified the most challenging passage points for
boat traffic. In all cases, we asked community
members to attribute their annotated pictures and
maps with flows from recent months, so that specific
flow levels associated with those dates could be
identified and incorporated into our environmental
flow prescription.
Based on a synthesis of information gathered in this
second workshop, we adjusted the unified
hydrograph created after the first workshop. This
resulted in our final recommended flow regime for
the Patuca River below the proposed Patuca 3,
which was formalized in a report that condensed all
findings from the field trips and workshops to justify
the ranges of recommended flow values, and
included a list of critical questions and research
priorities.
Feasibility Analysis of Flow Recommendations
Using daily discharge data for unregulated inflow
and simulated with-dam outflow, we developed a
simple spreadsheet model that estimated the
reservoir volume associated with alternative
operations scenarios. These operations scenarios
focused on regulated (derived from Sinotech’s
operations model and simulating the flow with dam
operations) and environmental flow regimes (the
regulated hydrograph with the recommended EFCs
added). To test the feasibility of implementing the
recommended EFCs we compared how the
regulated and environmental flow regimes affected
reservoir levels within the model. As a simple rule,
for the environmental flow regime the model
released high-flow pulses only after a high-flow
pulse entered the reservoir. High-flow pulses were
defined as sharp increases from base flow that
exceeded the lower boundary of the EFC magnitude
ranges for high-flow pulses (Table 1). After a highflow pulse entered the reservoir, the model released
a high-flow pulse that matched the magnitude and
duration of the inflow pulse up to the maximum
values of the recommended ranges for the EFCs
(Table 1). The model released high-flow pulses until
the maximum recommended number of pulses for
a wet year had been released. Thus, releasing highflow pulses within this model did not require a priori
designation of year type (e.g., dry, normal, wet), but
because the model released pulses based on inflow
events, the model did tend to release more pulses in
wet years than dry years.
RESULTS
Diverse data sources were used to develop flow
recommendations for the Patuca River below Patuca
3, including 29 years of hydrological records;
published and gray literature; TEK gathered in 24
interviews with 45 community members; direct
observation of channel morphology, forestry, and
agriculture; and the opinions of 18 specialists and
12 community leaders who participated in
workshops. Only those findings with direct
pertinence to the flow recommendation are
presented below.
Hydrological Analysis
Based on the analysis of annual flows within the 29year record, we identified four “dry” years (1973,
1985, 2000, and 2001) and six “wet” years (1979,
1982, 1993, 1995, 1998, and 1999). The remaining
19 years were classified as “normal.”
The IHA analysis for Cayetano indicated that the
greatest hydrological alterations with dam
operations will likely be: (1) a decline of high-flow
pulses during the wet season from an average of 10
per year to 5 per year; and (2) elevated low flows
during the dry season (Fig. 5). With unregulated
hydrology, base flows in March through May
averaged between 20 and 30 m3/s, whereas with
regulated hydrology, the base flows are predicted
to be between 65 and 70 m3/s as a result of releases
of water stored during the prior wet season to
generate electricity. Review of unregulated and
regulated hydrographs indicates that much of the
loss of high-flow pulses will occur in the transition
between the dry and wet seasons (e.g., June through
September) in the time that the reservoir refills after
the dry-season drawdown. Dam operations will
apparently have little or no effect on floods and late
wet-season flow levels (Fig. 5).
Over the 29-year hydrological record, approximately
one-third of the annual discharge at Kuhrpa was
derived from the portion of the watershed above
Cayetano (i.e., the portion of the drainage area above
the proposed dam). Only in the months of June and
July did more than half the flow at Kuhrpa derive
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Fig. 4. Important flow levels were established in workshops with community members by annotating
photographs of familiar locations along the river (top). In this case, a community member from Pimienta
Village is indicating the level that Hurricane Mitch reached by pointing out a specific palm tree that he
used as a visual reference during the storm. The results (bottom) helped establish the positive and
negative importance of different flow levels for values of the river from the perspectives of community
members.
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Table 1. Unified flow recommendation’s high-flow pulses and floods for dry, normal, and wet years.
EFC = environmental flow component.
EFC
Season
Year
type
Magnitude
(m3/s)
Frequency
Early wetseason highflow pulses
June 1–
July 15
Dry
Normal
Wet
Mid wetseason highflow pulses
July 16–
Nov. 14
Dry
Normal
Wet
125–170
125–300
125–500
≥1
≥2
≥2
4–10 d
Provide cues to migratory fish
Reduce predation on juveniles spawned
during dry season
≥4
≥4
≥4
4–10 d
Trigger spawning activity by migratory
fish
Fish gain access to channel margin habitat
Late wetseason highflow pulses
Nov. 15–
Dec. 15
Dry
Normal
Wet
125–170
125–300
150–350
≥1
≥2
≥2
Flood
Aug. 15–
Oct. 30
Dry
Normal
Wet
1000–2000
2000–3500
≥1
≥1
200–600
200–900
200–900
from above the dam site; for most months, the
proportion was approximately 20%. The IHA
analysis indicated that the primary hydrological
alteration likely at Kuhrpa is an increase in low
flows during the dry season, with relatively minor
or no effect on other flow components. Thus, the
aspects of our flow recommendations that address
high-flow pulses and floods pertain primarily to the
reach between the dam site and the confluence of
Rio Wampu (Fig. 1).
Aquatic Ecological Communities
Fisherman responses about aquatic community
composition and life-history traits were crossreferenced against existing species lists, published
literature, and the opinions of expert taxonomists
before the results presented here were finalized.
However, we do not consider this to be a definitive
list because we were unable to collect voucher
specimens to confirm species identities. Rather, we
consider this to represent a possible list of
commonly captured species that are likely to occur
Duration Example flow-ecology links
4–10 d
15–40 d
Migration and juvenile dispersal for latespawning fish
Replenish beaches for reptile nesting
Sediment transport and maintain channel
form
Create floodplain topography
Provide fish access to floodplain
Disperse tree seeds
Deposit sediment on agricultural fields
in the Patuca River. Twenty-six fish species in at
least 17 families were reported by community
members, and 17 non-piscine aquatic species were
reported to be important to communities (Table 2).
Most of these species were used as food sources,
indicating that the communities living in the middle
Patuca use a diversity of riverine animals for
subsistence. The most important species in the
fishery were the blackbelt cichlid (Vieja
maculicauda) and feral populations of nonindigenous African tilapia (from photo vouchers
appears to be Nile tilapia, Oreochromis niloticus).
Other important food fishes include the wolf cichlid
(Parachromis dovii), several snook species that
inhabit fresh water and salt water (Centropomus
undecimalis and C. ensiferus), and two mullet
species, the cuyamel (Joturus pichardi) and
tepemechín (Agonostomus monticola). A number of
non-piscine aquatic and semi-aquatic organisms are
also important to the human and biological
communities of the Patuca River. These include at
least three freshwater shrimp species, two crab
species, one mussel species (a food of last resort),
and a number of reptiles including the green iguana
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Fig. 5. Comparison of the median monthly flow values for the unregulated flow regime (green; error
bars bracket the middle third of the distribution) and the regulated (simulated) flow regime (black) at
Cayetano. The IHA analysis indicated that the greatest hydrological alterations will be elevated low
flows during the dry season, and a decline in high-flow pulses during the early part of the wet season
when the reservoir is filling to capacity.
(Iguana iguana) and five species of turtles that are
eaten by community members (Table 2).
Two characteristics of the aquatic communities
identified in workshops as highly important to the
creation of a flow prescription for Patuca 3 were:
(1) migratory life cycles of fishes; and (2)
reproductive timing and habitats of fishes and
herpetofauna. At least eight of the species reported
are migratory with life cycles that integrate
freshwater and saltwater environments (Table 2).
Of these, four have catadromous life cycles where
the adults live in freshwater and migrate to the coast
to spawn and then either die (as does the American
eel, A. rostrata) or migrate back upstream (as does
cuyamel). The other four migratory species have
amphidromous life cycles where the adults live
entirely in freshwater, but lay eggs that are carried
by the river to hatch in or just upstream of the
estuary, where the young feed until they migrate
upstream to live the rest of their lives in freshwater
(McDowall 1992). All of these species occupy large
headwater streams as adults, and thus require
unimpeded migration corridors between the
mountains and the sea to persist in upstream habitats
(March et al. 2003). Based on research elsewhere
in the region, spawning and downstream migration
of the species in the study area are thought to
correspond with wet-season flood events (Cruz
1987, 1989, Benstead et al. 1999, 2000), and
upstream post-larval migration has been documented
to occur in large mixed-species aggregations in the
transition between the wet and dry season (Gilbert
and Kelso 1971, Winemiller and Leslie 1992).
Based on this knowledge of life histories, we
identified three aspects of flow to which migratory
fauna were likely to be most sensitive: (1) the timing
of transitions between the dry and wet season and
the onset of flooding; (2) the magnitudes of dry and
wet season base flows and high flow events; and (3)
the variability of flow conditions in the early wet
season that may serve as cues for migrations.
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Table 2. Fish species and some of the other aquatic organisms reported by the fishermen interviewed, with
information on their reproductive habits, migratory status, and importance to local fisheries. Fisheries codes
are: rarely captured (R), occasionally captured (O), seasonally important (S), and commonly captured (C).
Family
Scientific name
Common name
Reproduce
when?
Reproduce where?
Migratory?
Fishery
Carcharhinidae Carcharhinus leucas Bull shark
?
Sea
No
R
Pristidae
Pristis pristis
Common
sawfish
?
?
No
R
Anguillidae
Anguilla rostrata
American eel
Sea
Catadromous
O
Sea
No
O
?
No
O
Megalopidae Megalops atlanticus
Tarpon
Characidae
Astyanax aeneus
Central tetra
Ictaluridae
Ictalurus furcatus
Blue catfish
June–Aug.,
Nov.–Jan.
?
Pimelodidae Rhamdia spp.
Chulin
June–Aug.
?
No
C
Poeciliidae
Molly
All year; peak
May–June
?
No
S
Centropomidae Centropomus
ensiferus
Swordspine
snook
Eggs Oct.–Jan.
Sea
No
C
Centropomidae Centropomus
undecimalis
Common snook
Eggs Oct.–Jan.
Sea
No
C
Lutjanidae
Lutjanus griseus
Gray snapper
?
?
Sea
O
Gerreidae
Eugerres spp.
Mojarra
?
?
No
O
Haemulidae
Pomadasys crocro
Burro grunt
?
?
Amphidromous
O
Cichlidae
Amhpilophus alfari
Pastel cichlid
Feb.–April
River banks
No
O
Cichlidae
Amphilophus
longimanus
Red breast
cichlid
Feb.–April
River banks
No
C
Cichlidae
Archocentrus
spilurus
Blue eye cichlid
Feb.–April, May
River banks
No
O
Cichlidae
Herotilapia
multispinosa
Rainbow cichlid
Feb.–April
River banks, creeks
No
?
Cichlidae
Oreochromis
niloticus
Nile tilapia
Feb.–April
River banks
No
C
Cichlidae
Parachromis dovii
Wolf cichlid
Feb.–April
River banks
Local
movements
C
Cichlidae
Parachromis
managuensis
Jaguar cichlid
Feb.–April
River banks, creeks
No
O
Poecilia gilli
?
No
C
(con'd)
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Cichlidae
Vieja maculicauda
Blackbelt cichlid
Feb.–April
River banks, creeks
No
C
Mugilidae
Agonostomus
monticola
Mountain mullet
Eggs in dry, go
to sea in wet
Puts eggs under
rocks
Catadromous
and/or
amphidromous
S
Mugilidae
Joturus pichardi
Bobo mullet
Eggs in dry,
migrate Aug.–
Sep.; return Nov.
Estuary
Catadromous
S
Eleotridae
Gobiomorus
dormitor
Bigmouth
sleeper
Eggs in dry
Deep pools
Amphidromous
O
Gobiidae
Awaous banana
Green river goby
?
Deep pools
Amphidromous
O
Palaemonidae Macrobrachium
carcinus
Macrobrachium
Wet season
Amphidromous
O
Atyidae
Atya sp.
Atyid shrimp
Wet season
Amphidromous
?
Portunidae
Callinectes sp.
Crab
Non-fish taxa
Gecarcinidae Cardisoma guanhumi Land crab
O
June
Streams
?
O
Alligatoridae Caiman crocodilus
Spectacled
caiman
?
Exposed sand bars
near river
No
?
Crocodylidae Crocodylus acutus
Crocodile
Dry
Exposed sand bars
near river
No
?
Kinosternidae Kinosternon
leucostomun
Wood turtle
?
Emydidae
Rhinoclemmiys
funera
White-lipped
mud turtle
S
Emydidae
Trachemys scripta
Jicotea
S
Iguanidae
Iguana iguana
Green iguana
Interviews with fishermen revealed important
patterns in the reproductive habitats and times of
reproduction for many aquatic organisms in the
Patuca River. Most of aquatic species identified
from the middle Patuca were reported to either
reproduce during the dry season or to have eggs in
development within the body during this period
(Table 2). Species reported to reproduce during the
dry season include all of the fishes in the family
Cichlidae, as well as turtles, iguanas, and crocodiles.
Turtles were reported by almost all respondents to
reproduce on sand bars in the river channel in the
month of February, whereas iguanas were reported
March
Exposed sand bars No
near river
S
to nest on bars in March. Given the prediction of
higher dry-season base flows, the availability of
nesting beaches for these reptiles may become more
limited. All cichlids in the study area (except tilapia)
are nest brooders, where adult breeding pairs create
and defend nests near the banks where their eggs
and young develop. Should peaking flows be
released from the Patuca 3 dam to generate
electricity during times of greatest electricity
demand, bank habitats will experience rapid daily
fluctuations in water levels, potentially disrupting
nesting environments. From these findings, we
identified two additional aspects of flow likely to
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be important to maintenance of aquatic
communities: (1) timing of dry-season base flows;
and (2) dry-season daily flow variability potentially
associated with peaking operation. Officials of
ENEE were uncertain about the degree to which
daily peaking operations will occur, so we drafted
general guidelines to address peaking operation as
a precaution (not presented here).
Importance of Floodplains
Communities living along the Patuca River
downstream of the dam site use floodplains heavily
for agricultural activities and collection of useful
plants and forest products. Most of the important
staple and cash crops are planted on the floodplain
within the area that is periodically inundated by
floodwaters. These include bananas, plantains, rice,
beans, and cacao. The annual crops are planted at
specific times of year in response to the annual cycle
of drought and rains. Community members reported
both positive and negative interactions between
river flows and agricultural productivity. Positive
influences include the deposition of nutrient-rich
sediments during wet-season floods that increase
the fertility of floodplain fields. For example, the
agricultural working group during the second
workshop reported that flooding in October was
correlated with good harvests of beans in the
following April. Floods were also observed to
reduce fungi that attack cacao trees. However, it was
reported that large floods can be detrimental in that
they can damage crops planted near the river,
particularly maize, bananas, and rice. Because
Patuca 3 is not intended to provide flood control,
which was confirmed by the IHA analysis showing
no change in flood magnitudes or frequencies
between the unregulated and regulated flow
regimes, the dam is unlikely to reduce the damages
associated with large flood events.
Transportation
According to boat captains and community leaders,
about 60% of boat traffic on the Patuca River is for
business and trade, 30% is for public transportation,
and the remaining 10% is for other travel. River
trade takes place throughout the year. In the dry
season, low river levels can make travel difficult
and expensive. Low water levels cause trips to
become much longer and introduce the possibility
of damaging boats and engine propellers on
boulders and exposed logs, and causing injury or
death to passengers. The economic livelihoods of
the communities of the middle Patuca are tied to
their ability to transport goods on the river, thus the
number of trips in the dry and wet seasons were
reported to be roughly equal, although the seasonal
variation of prices of the various products (butter,
oil, tomato paste, soft drinks, etc.) do reflect the
difficulties of navigating the river during the dry
season.
Participants in the transportation working group
identified six critical points of passage and
numerous smaller challenges between Kuhrpa and
Nueva Palestina. All but one of these obstructions
were attributable to low water levels during the dry
season. It was reported that a 1–2 m augmentation
of flow levels above normal dry-season base flow
level would be necessary to overcome these difficult
barriers to passage and trade. In flow quantities, this
translates to an increase of the mean dry-season base
flow (range = 20–30 m3/s at Cayetano) by 40–50
m3/s to approximately 60–80 m3/s. This 60–80 m3/
s range is similar to the predicted mean outflow from
Patuca 3 during normal dry-season operation,
suggesting that the dam may have a positive
influence on transportation.
Robustness of TEK
It is important to examine the robustness of the TEK
gathered and to identify potential biases that may
affect our conclusions. Of particular importance are:
(1) the accuracy of the facts shared by respondents,
and (2) the variability of responses between
individuals and communities. It is possible to assess
the accuracy of some responses by cross-checking
interview data against published scientific accounts.
When we did this for fish life-history data, we
concluded that fishermen were best at identifying
ecological characteristics that are readily
observable (e.g., they take place during the dry
season when river water is clear), or that concern
species that have high use value. For example, more
than 80% of respondents correctly identified
commonly captured resident cichlid fishes as
reproductively active in the dry season, and more
than 50% reported that tarpon and the two snook
species originated in the sea and traveled long
distances in the river channel. Yet, only one-third
of respondents correctly identified tepemechín and
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cuyamel (both important food fishes) as animals that
migrate during the wet season (Cruz 1987, 1989),
and none accurately identified the other known
migratory fishes and shrimps (Table 2). The failure
to identify these species as migratory may be due to
the fact that all of these species are amphidromous
(so the adults are permanent residents of river
habitats), that some of these species are cryptic, or
that fishermen are unaware of what these fishes do
when the water becomes turbid. Thus, without
complementary knowledge from published reports
and expert consultation, use of TEK alone would
have led to a less complete understanding of
important ecological traits of aquatic biota.
Nevertheless, the knowledge gained from TEK was
still of sufficient quality to formulate reasonable
hypotheses about links between river flow and biota.
The variability of responses between interviews was
subject dependent, but tended to vary little between
individuals, ethnicities, or communities. For
instance, the fundamental observations about where
crops were located relative to the river channel,
where major barriers to transportation were located,
and what fishes were important varied little. Over
85% of respondents to agriculture surveys
commented on the importance of flood sediments
for fertilizing crops on the floodplain. More varied
responses were recorded on more nuanced questions
such as, “At what river level do floods become
detrimental?” Nonetheless, much of the basic
information used in the development of our
environmental flow recommendations was collected
within the first eight to ten interviews. More
interviews after this served to (1) reinforce the
information gained previously, and (2) provide
insights into less obvious aspects ecosystems or
flow links. Examples of insights gained from single
respondents included the observation that floods
help remove pests from cacao fields, and that the
common sawfish (Pristis pristis) occurred in the
Patuca River as recently as the early 1980s.
Although important, these observations were not
necessary to hypothesize the environmental flow
links that were ultimately most useful to our
recommendations.
Flow Recommendations
The unified flow recommendation was defined in
terms of EFCs—including low flows for each
month, high-flow pulses, and floods—that varied
for dry, normal, and wet years. Each
recommendation was based upon a hypothesized
link between a given EFC and specific processes or
resources in the river ecosystem (Tables 1 and 3,
Fig. 6).
Feasibility Analysis
In all years except one, the spreadsheet model
indicated that the reservoir would fill early in the
wet season (15 August ± 8 d; mean and standard
error). Thereafter, the daily flow would become runof-the-river (e.g., outflow equals inflow). Because
of this trend, in nearly all years the regulated
hydrograph is predicted to provide all the
recommended floods and late wet-season high-flow
pulses.
With regulated hydrology, middle wet-season highflow pulses are predicted to occur less frequently
than they did naturally (Fig. 7). The recommended
number of middle wet-season high-flow pulses
occurred in 12 out of the 29 years of the simulated
regulated flow record, suggesting that an
environmental flow regime will need to add at least
one middle wet-season high-flow pulse in
approximately 60% of years. Dam operations are
predicted to have a greater proportional impact on
early wet-season high-flow pulses (Fig. 7). Whereas
in the unregulated flow regime, at least two early
wet-season pulses occurred in 83% of years, with
regulated hydrology two of these events are
predicted to occur in only 17% of years, and 70%
of years are predicted to have no early wet-season
high-flow pulse whatsoever.
Because early and middle wet-season high-flow
pulses were predicted to be the EFCs most affected
by dam operations (other than dry season low
flows), we focused the feasibility analysis on these
events. The spreadsheet model indicated that, in all
but two years, adding the recommended number of
early and middle wet-season high-flow pulses to the
regulated hydrograph would have delayed the
refilling of the reservoir (and onset of run-of-river
conditions) by less than 8 d (Fig. 8). In the seconddriest year on record, releasing the recommended
number of high-flow pulses would have delayed
reservoir refilling by 14 d. The driest year on record
(2001) was the only one in which the reservoir was
not predicted to refill with the regulated flow
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Table 3. Unified flow recommendation’s low flows for each month, for dry, normal, and wet years. Flow
rates are cubic meters per second (m3/s).
Year Type
Month
Dry
Normal
Wet
January
40–50
50–65
65–80
Jan. wet-year range considered “optimal” for
transportation
Beaches used by reptiles for nesting
February
30–35
35–50
55–65
Beaches used by reptiles for nesting
March
30
30–40
40–45
Flows below 30 m3/s make transportation very
difficult
Cichlid fish spawning
April
30
30
30
Cichlid fish spawning
May
30
30
30–35
Cichlid fish spawning
June
30–35
35–60
70–90
Cues for spawning migratory species
July
45–55
60–90
125–135
Cues for spawning migratory species
August
45–70
80–115
120–150
September
60–80
80–120
130–145
October
90–100
100–130
130–145
November
60–75
80–115
120–140
December
45–60
65–85
85–120
regime. With 2001 hydrology, the reservoir releases
would have passed below the threshold for power
generation, and essentially become run-of-the-river
with low flows on 4 February 2002. If an
environmental flow regime had been released in
2001, this condition would have been reached on 5
January 2002. In both scenarios, the reservoir was
predicted to begin generation on the same day (25
May 2002) and refill and become run-of-river on
the same day (29 August 2002). Thus, in only 1
month of 1 year out of 29 years did releasing an
environmental flow regime substantially affect
simulated hydropower generation, as it increased a
period of no generation from 110 d to 140 d.
Example flow-ecology links
Upstream migrations of juvenile migratory
species may begin
DISCUSSION
The multi-step process used to define an
environmental flow prescription for the Patuca 3
dam linked patterns of historical flow with human
values of the river and factors hypothesized as
important for maintaining ecosystems, traditional
economies, and cultural uses. Traditional ecological
knowledge was essential to this process. The use of
traditional and local ecological knowledge to form
biological hypotheses and guide water resource
management efforts has many precedents. For
instance, Robertson and McGee (2003) used oral
history data collected from local residents and
natural resource managers to assemble a historical
record of flood frequencies and ecology of a wetland
in Australia, which were used to define scenarios
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Fig. 6. A graphical summary of our environmental flow recommendation (dark black line) for a
“normal” hydrological year. Flow magnitudes are shown on the y-axis, with month shown on the x-axis.
Dry and wet seasons are indicated by white and gray shaded areas, respectively. Environmental flow
components (base flow, high flow pulses, and floods) are labeled with some details of the important
ecological and social values that they support. Ideally, the timing of flow pulses and floods will be
adjusted as a function of reservoir inflow, rather than having the static shape presented here as an
example.
for environmental decision support. The government
of British Columbia, Canada drew extensively on
local knowledge and expert opinion from public,
aboriginal, and regulatory agency stakeholders to
examine water allocation at 22 major hydropower
sites, and to help select operating alternatives for
dams (Failing et al. 2007). In fisheries management,
fact-based knowledge from local and aboriginal
fishermen has been shown to complement fisheries
science by providing concordant and additional
information about fish community composition,
population viability, breeding and migration
patterns, and behavioral ecology (Johannes 1978,
1981, Neis et al. 1999, Aswani and Hamilton 2004,
Fraser et al. 2006, Garcia-Quijano 2007). Our
environmental flow prescription was guided by the
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Fig. 7. Frequency of early and middle wet-season high-flow pulses with the unregulated flow regime
(gray bars) and the regulated flow regime (i.e., planned dam operations without releasing environmental
flow recommendations). Error bars represent the standard error.
fact-based claims about riverine biota shared by the
indigenous communities of the Patuca River, and
by the value-based statements of how the river is
important to communities.
Relative to the dominant paradigm of hypothesis
testing using the scientific method, local and
traditional ecological knowledge may seem
subjective and uncertain. A substantial body of
research identifies the limitations of humans to
accurately translate their experiences into explicit
information (Sterman 2000 in Fazey et al. 2006),
because of human tendencies toward judgmental
biases, difficulties in understanding complex
probabilities, and limited abilities to learn about
complex systems (Fazey et al. 2006). Bias can also
arise when information providers desire specific
outcomes that may be directly affected by the
information they provide (Fazey et al. 2006). In our
study, at least four factors may have affected the
quality of information that we received. First,
research visits to communities were relatively brief,
averaging no more than 3 d in any one community.
Second, ENEE’s past activities in the region,
particularly their earlier attempts to develop another
dam on the Patuca River main stem (a project that
was strongly opposed by the communities of the
middle Patuca; Gordon 2002) may have led to a
strained context for gathering information. This
tension was evident in public meetings that were
held to describe the Patuca 3 project, but entered
overtly into the interviews with fewer than eight of
the 45 respondents. Third, all interviews were
carried out in Spanish, the second language of the
majority of respondents, whose primary languages
were Miskitu or Tawahka. Interviewers were
careful to seek clarification when difficulties arose,
but this still may have led to translation errors.
Finally, three-quarters of respondents were male,
and thus our sample of river values reflects a genderbiased sample.
Researchers using TEK as an information source
can guard against bias in numerous ways. These
include subjecting information to scrutiny by an
extended peer group, use of structured elicitation
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Fig. 8. Results of our reservoir-filling mass-balance model. Top graph shows hydrology for 1985 (one of
the driest years in the record), showing unregulated (inflow to reservoir; light gray), regulated (simulated
outflow with dam operation; thick blue), and reservoir storage deficit (thin black line). The bottom graph
shows an implementation scenario for an environmental flow regime for the same year that includes two
early wet-season high-flow pulses (in solid circle) and three mid wet-season high-flow pulses (within
dashed circles). These pulses delay reservoir filling by only 8 d. The red arrow indicates the day that the
reservoir would have refilled under the regulated flow regime, and the black arrow indicates the day the
reservoir would have refilled under the recommended environmental flow regime. MCM = million cubic
meters.
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methods, and gathering data in a way that separates
direct observations (fact-based claims) from
inference and value-based claims (Huntington
2000, Failing et al. 2007). In our study, we used a
structured interview to collect factual information
about river hydrology, geomorphology, and
ecology. Our interviews were often done in a small
group setting, which led to a limited form of scrutiny
by peers, and workshops provided another forum
for scrutiny by an extended peer group (Huntington
2000, Failing et al. 2007). We also subjected our
species lists to review by taxonomists familiar with
local biota. A cursory verification of the TEK
gathered against factual reports from the scientific
literature showed a relatively high degree of
accuracy about those ecosystem characteristics that
(1) were readily observable; and (2) about species
with high use value. Within the communities of the
middle Patuca River, variability between responses
about the links among the river, flow patterns, and
human well-being was relatively low, suggesting
that our final environmental flow recommendation
would have been substantially similar if only half
the number of interviews had been conducted.
Nonetheless, more interviews continued to
strengthen our picture of how river flow influenced
communities and ecosystems, thus we suggest that
more interviews are still preferred when possible.
The use of TEK to formulate an environmental flow
prescription was the only feasible option in this case
to allow us to overcome the relative paucity of
empirical scientific information for the study area,
and to incorporate values of river-dependent
communities into our recommendations. The factbased claims that we recorded gave us the ability to
assemble a set of ecological hypotheses, which were
strengthened with input from local and international
scientists. TEK also gave us detailed information
about the social and economic values of the river
and its hydrology to the people whose lives and
livelihoods will be the most affected by the
construction of Patuca 3. To complement the
information generated through TEK, we drew on
expert knowledge and used several simple but
powerful assessment tools—IHA, HEC-RPT, and a
spreadsheet reservoir model—to help us discern
conflict areas and explore scenarios and solutions.
Our product is a highly replicable example of how
the Savannah Process can be applied in a data-poor
context in a way that is responsive to the ecological
and social realities of a specific place.
CONCLUSION: ENVIRONMENTAL FLOWS
AND SUSTAINABLE HYDROPOWER
By combining TEK with several analytical tools
within a flexible and adaptive process (Richter et al.
2006), we overcame limitations of scientific
information to develop an environmental flow
regime for the Patuca River below a proposed
hydropower dam. This approach can be adapted for
use at the numerous dams that already exist or are
under development in this region and around the
world that share similar data limitations. However,
as explained below, ensuring the sustainability of
future hydropower development in Central America
will require more than the prescription and
implementation of environmental flow regimes.
Assuming that our environmental flow recommendation
is included in operations of the Patuca 3 dam, it will
maintain important features of the natural
hydrograph. This is a significant accomplishment
in the search for solutions that manage water for
people and nature. However, these recommendations
—focused on a single river reach below a single
proposed dam—reveal numerous limitations for
pursuing sustainable hydropower at the scale of an
individual hydropower project. For example,
participants identified several potential impacts
from the dam that environmental flows can only
partially mitigate or cannot address at all. These
impacts include barriers to fish migration into the
upper watershed, capture of sediment, organic
material, and nutrients within the reservoir, and
changes to water quality and water temperatures.
Impacts to migratory biota are a particularly serious
issue in terms of potential effects on riverine biota
and human communities. Patuca 3 will create a large
barrier in the channel that will exclude migratory
species from a significant percentage of their range
in the watershed (approximately half the watershed
lies above the dam site). Possible results of the
barrier include local extirpation of these species
from the watershed above the dam (Holmquist et al.
1998, Greathouse et al. 2006) and reduced
population size and/or genetic diversity, and thus
reduced population viability (Shaffer 1981) of these
species at the basin scale. Unfortunately, there is
almost no available information on the relative
importance of habitat above the dam site to
migratory species, and so the degree that the dam
will affect migratory species cannot be predicted
accurately.
Ecology and Society 15(1): 6
http://www.ecologyandsociety.org/vol15/iss1/art6/
These issues emphasize the inherent limitations of
pursuing sustainable hydropower at the scale of a
single dam project. To fully address and mitigate
the range of impacts caused by dam development,
sustainable hydropower must be pursued across
many project sites at larger spatial scales, such as
an entire river basin or region (Harrison et al. 2007).
Although the concept of sustainable hydropower is
relatively new and still being debated, initial
definitions from a wide range of sources support
this assertion. For example, Ledec and Quintero
(2003) emphasize that good site selection is by far
the most effective form of “mitigation” for new
dams. This acknowledges the limitations for dams
to address impacts locally (e.g., impacts on
migratory fish) and, therefore, the analysis of site
selection should encompass a large spatial area to
direct dam development toward the least damaging
locations. The International Hydropower Association’s
Sustainable Assessment Protocol, which includes
20 criteria for evaluating new hydropower dams,
also emphasizes the importance of taking a regional
approach to site selection, such as avoiding river
reaches with important environmental and cultural
values, and favoring lower-value river reaches or
those with flows already regulated by dams for
development (International Hydropower Association
2006).
We suggest that much greater integration of
conservation and infrastructure planning will be
necessary to maximize the environmental and social
sustainability of the proposed expansion of
hydropower in Central America, and that
environmental flow regimes are only one piece of
a larger puzzle. Attempting to address issues of
sustainability at the scale of individual dams, while
ignoring larger geographic perspectives, will only
slow, but not prevent, the continued degradation of
aquatic ecosystems and resources that support
biodiversity and rural and indigenous communities.
Furthermore, an emphasis on the site scale misses
opportunities that will benefit conservation,
communities, and even hydropower developers. For
example, hydropower development planning that is
integrated with conservation planning can allow
individual projects to contribute toward regional
conservation goals as part of their mitigation
strategies, thus achieving economies of scale not
possible at the site scale. Hydropower projects
selected through such a process are likely to face
less controversy and opposition and thus have
greater certainty and security for investors,
developers, and governments.
Responses to this article can be read online at:
http://www.ecologyandsociety.org/vol15/iss1/art6/responses/
Acknowledgments:
We wish to extend our appreciation for the support
given by a number of staff from The Nature
Conservancy representing a variety of organizational
perspectives (Julio Carcamo, Nicole Silk, and Brian
Richter), staff from ENEE (Ing. Sergio Chavez, Dr.
Roberto Avalos, Cristian Andino, Irma Ayes
Rivera), as well as outside experts from Honduras
(especially Lic. Ester López Irías), Central
America, and the United States. Jorge Jiménez
(Organization for Tropical Studies), and Elizabeth
Anderson (Field Museum of Natural History)
helped facilitate the first workshop, and Brian
Richter and Nicole Silk of TNC, Kendra
McSweeney, and Will Matamoros provided
constructive reviews of this manuscript. We are
particularly grateful for the significant contributions
of time and information by the indigenous
communities along the Patuca River. This product
and the extensive exchanges and interactions it
represents would not have been possible without
significant financial and personnel contributions
from both TNC and ENEE.
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Appendix 1. Standard questionnaire used to interview community leaders and fisherpersons.
Please click here to download file ‘appendix1.pdf’.