Frequent and prolonged droughts challenge groundwater sustainability in California but managing aquifer recharge can help to partially offset groundwater overdraft. Here, we use managed aquifer recharge (MAR) to examine potential benefits... more
Frequent and prolonged droughts challenge groundwater sustainability in California but managing aquifer recharge can help to partially offset groundwater overdraft. Here, we use managed aquifer recharge (MAR) to examine potential benefits of adding an artificial recharge facility downstream from California’s Lower American River Basin, in part to prepare for drought. We use a statewide hydroeconomic model, CALVIN, which integrates hydrology, the economics of water scarcity cost and operations, environmental flow requirements, and other operational constraints, and allocates water monthly to minimize total scarcity and operating costs. This study considers a recharge facility with unconstrained and constrained flows. The results show that adding a recharge facility increases groundwater storage, reduces groundwater overdraft, and increases hydropower without substantially impacting environmental flows. Further, artificial recharge adds economic benefits by (1) reducing the combined c...
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This study developed and applied a novel basin-scale, daily time step, rule-based water system simulation model that includes hydroeconomic optimization for hydropower production with a hydroeconomic optimization component that... more
This study developed and applied a novel basin-scale, daily time step, rule-based water system simulation model that includes hydroeconomic optimization for hydropower production with a hydroeconomic optimization component that incorporates wholesale electricity prices from the day-ahead market known as CenSierraPywr. High elevation reservoirs are typically operated to maximize revenue from hydropower production, while meeting the legal and contractual obligations for water requirements downstream and, in many cases, restrictions on certain environmentally harmful operations. Wholesale hourly electricity prices in the day ahead market drive much of the decision-making process in releasing water from reservoirs for hydropower production, though other economic incentives for ancillary services are also important. Hourly energy prices are used to develop piecewise linear price curves that are used by the CenSierraPywr routine. Ancillary services were not included other than spinning re...
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Freshwater aquatic ecosystems are highly sensitive to flow regime alteration caused by anthropogenic activities, including river regulation and atmospheric warming-induced climate change. Either climate change or reservoir operations are... more
Freshwater aquatic ecosystems are highly sensitive to flow regime alteration caused by anthropogenic activities, including river regulation and atmospheric warming-induced climate change. Either climate change or reservoir operations are among the main drivers of changes in the flow regime of rivers globally. Using modeled unregulated and simulated regulated streamflow under historical and future climate scenarios, this study evaluated potential changes to the flow regime due to climate change and reservoir operations for the major tributaries of the San Joaquin River Basin, California United States. We selected a set of Indicators of Hydrologic Alteration (IHA) to evaluate historical and projected future trends of streamflow dynamics: rise and fall rates, durations and counts of low and high pulses, and the magnitude of extremes. Results show that most indicators have pronounced departures from baseline conditions under anticipated future climate conditions given existing reservoir...
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Changing climate signals and the continuous world population growth requires proper hydrologic risk analysis to build and operate water resource infrastructures in a sustainable way. Although modernized computational facilities are... more
Changing climate signals and the continuous world population growth requires proper hydrologic risk analysis to build and operate water resource infrastructures in a sustainable way. Although modernized computational facilities are becoming popular to understand complex systems, there is not a proper approach for the space – time analysis of extreme rainfall events. Many statistical approaches have been suggested to describe the space–time structure of rainfall; nevertheless, none of them is good enough to represent, for all observational scales, the geometrical structure observed in either rainfall time series or rainfall-derived spatial fields. This research presents a geometric approach to understand the intensity – area – duration – frequency (IADF) relationship without losing information or statistical assumptions. Moreover, this study introduces a promising conceptualization about how understand the space–time structure of rainfall via codimension functions and dynamic scaling...
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Research Interests: Environmental Engineering, Civil Engineering, Computer Science, Algorithms, Machine Learning, and 15 moreHydrology, Computational Intelligence, Performance, Neural Networks, Artificial Neural Networks, Models, Flow, Hydrological modelling, Performances, Artificial Neural Network, Hydrological Processes, K Nearest Neighbour, Gaussian kernel, Drainage Basins, and hydrologic model
Research Interests: Biology and Agroforestry
Research Interests: Environmental Engineering, Civil Engineering, Computer Science, Algorithms, Machine Learning, and 15 moreHydrology, Computational Intelligence, Performance, Neural Networks, Artificial Neural Networks, Models, Flow, Hydrological modelling, Performances, Artificial Neural Network, Hydrological Processes, K Nearest Neighbour, Gaussian kernel, Drainage Basins, and hydrologic model
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A deterministic geometric approach, the fractal–multifractal (FM) method, useful in modeling storm events and recently adapted in order to encode highly intermittent daily rainfall records, is employed to study the complexity of rainfall... more
A deterministic geometric approach, the fractal–multifractal (FM) method, useful in modeling storm events and recently adapted in order to encode highly intermittent daily rainfall records, is employed to study the complexity of rainfall sets within California. Specifically, sets—from south to north—at Cherry Valley, Merced, Sacramento and Shasta Dam and containing, respectively 59, 116, 115, and 72 years, all ending at water year 2015, are studied. The analysis reveals that: (a) the FM approach provides faithful encodings of all records, by years, with mean square and maximum errors in accumulated rain that are less than a mere 2 and 10%, respectively; (b) the evolution of the corresponding “best” FM parameters, allowing visualization of the inter-annual rainfall dynamics from a reduced vantage point, exhibit a highly entropic variation that prevents discriminating between sites and extrapolating to the future; and (c) the rain signals at all sites may be termed “equally complex,” ...
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California's agricultural sector is the highest valued agricultural sector in the United States. It is also a global leader in the production of various specialty crops, including three major tree nuts - almond, walnut, and pistachio.... more
California's agricultural sector is the highest valued agricultural sector in the United States. It is also a global leader in the production of various specialty crops, including three major tree nuts - almond, walnut, and pistachio. These three nut crops accounted for approximately 16% of the state's total agricultural economy. Current and future changes in climate pose many challenges in agriculture and impacts related to increased pest pressure in agriculture due to elevated temperatures are significant. The navel orangeworm, Amyelois transitella (Walker), is the most challenging pest of tree nuts in California and often cause a significant economic loss despite the careful implementation of multiple pest control tactics. Temperature variations can directly affect the developmental rates, behavior, and overall population dynamics of this pest, and it is critically important to understand these dynamics with respect to climate change. The objective of this study was to qu...
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Connections are ubiquitous in hydrology. However, understanding the nature and extent of connections in hydrologic systems has and continues to be a tremendous challenge. In recent years, applications of the concepts of complex networks... more
Connections are ubiquitous in hydrology. However, understanding the nature and extent of connections in hydrologic systems has and continues to be a tremendous challenge. In recent years, applications of the concepts of complex networks to study connections in hydrologic systems have started to emerge. This chapter aims to offer an overview of the science of complex networks and its applications in hydrology. First, the basic concept of a network, the history of development of network theory, and some important measures of network properties are presented. Next, applications of complex networks in hydrology are reviewed, including studies on spatial connections, temporal connections, and catchment classification. Finally, some remarks on future directions are made.
Frontline communities of California experience disproportionate social, economic, and environmental injustices, and climate change is exacerbating the root causes of inequity in those areas. Yet, climate adaptation and mitigation... more
Frontline communities of California experience disproportionate social, economic, and environmental injustices, and climate change is exacerbating the root causes of inequity in those areas. Yet, climate adaptation and mitigation strategies often fail to meaningfully address the experience of frontline community stakeholders. Here, we present three challenges, three errors, and three solutions to better integrate frontline communities' needs in climate change research and to create more impactful policies. We base our perspective on our collective firsthand experiences and on scholarship to bridge local knowledge with hydroclimatic research and policymaking. Unawareness of local priorities (Challenge 1) is a consequence of Ignoring local knowledge (Error 1) that can be, in part, resolved with Information exchange and expansion of community-based participatory research (Solution 1). Unequal access to natural resources (Challenge 2) is often due to Top-down decision making (Error ...
A surface energy balance model was conceived to estimate crop transpiration and soil evaporation in orchards and vineyards where the floor is partially wetted by micro-irrigation systems. The proposed surface energy balance model for... more
A surface energy balance model was conceived to estimate crop transpiration and soil evaporation in orchards and vineyards where the floor is partially wetted by micro-irrigation systems. The proposed surface energy balance model for partial wetting (SEB-PW) builds upon previous multiple-layer modelling approaches to estimate the latent, sensible, and soil heat fluxes, while partitioning the total evapotranspiration ( E T ) into dry and wet soil evaporation ( λ E s o i l ) and crop transpiration ( T ). The model estimates the energy balance and flux resistances for the evaporation from dry and wet soil areas below the canopy, evaporation from dry and wet soil areas between plant rows, crop transpiration, and total crop E T . This article describes the model development, sensitivity analysis and a preliminary model evaluation. The evaluation shows that simulated hourly E T values have a good correlation with field measurements conducted with the surface renewal method and micro-lysim...
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Strawberry is a high value and labor-intensive specialty crop in California. The three major fruit production areas on the Central Coast complement each other in producing fruits almost throughout the year. Forecasting strawberry yield... more
Strawberry is a high value and labor-intensive specialty crop in California. The three major fruit production areas on the Central Coast complement each other in producing fruits almost throughout the year. Forecasting strawberry yield with some lead time can help growers plan for required and often limited human resources and aid in making strategic business decisions. The objectives of this paper were to investigate the correlation among various weather parameters related with strawberry yield at the field level and to evaluate yield forecasts using the predictive principal component regression (PPCR) and two machine-learning techniques: (a) a single layer neural network (NN) and (b) generic random forest (RF). The meteorological parameters were a combination of the sensor data measured in the strawberry field, meteorological data obtained from the nearest weather station, and calculated agroclimatic indices such as chill hours. The correlation analysis showed that all of the para...
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In California, a significant percentage of the pistachio acreage is in the San Joaquin Valley on saline and saline-sodic soils. However, irrigation management practices in commercial pistachio production are based on water-use information... more
In California, a significant percentage of the pistachio acreage is in the San Joaquin Valley on saline and saline-sodic soils. However, irrigation management practices in commercial pistachio production are based on water-use information developed nearly two decades ago from experiments conducted in non-saline orchards sprinkler-irrigated with good quality water. No information is currently available that quantify the effect of salinity or combined salinity and sodicity on water use of micro-irrigated pistachio orchards, even though such information would help growers schedule irrigations and control soil salinity through leaching. To fill this gap, a field research study was conducted in 2016 and 2017 to measure the actual evapotranspiration (ETa) from commercial pistachio orchards grown on non-saline and saline-sodic soils in the southern portion of the San Joaquin Valley of California. The study aimed at investigating the functional relations between soil salinity/sodicity and t...
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Abstract A deterministic geometric approach, the fractal-multifractal (FM) method, is proposed to temporally downscale (disaggregate) rainfall and streamflow records. The applicability of the FM approach is tested on: (1) two sets of... more
Abstract A deterministic geometric approach, the fractal-multifractal (FM) method, is proposed to temporally downscale (disaggregate) rainfall and streamflow records. The applicability of the FM approach is tested on: (1) two sets of rainfall records—one from Laikakota, Bolivia and the other from Tinkham, Washington, USA; and (2) two distinct sets of streamflow records—for water years 2005 and 2008 from the Sacramento River, California, USA. For the purpose of validation, the available daily records are first aggregated into weekly, biweekly, and monthly records and then the FM method is applied to downscale such sets back into the daily scale. The results indicate that the FM method, coupled with a threshold to capture the high intermittency of rainfall and a smoothing parameter to get the milder texture of streamflow, readily generates daily series (over a year) based on weekly, biweekly, and monthly accumulated information, which reasonably preserves the time evolution of the records (especially for streamflow) and captures a variety of key statistical attributes (e.g., autocorrelation, histogram, and entropy). It is argued that the FM deterministic downscalings may enhance and/or supplement available stochastic disaggregation methods.
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Application of a deterministic geometric approach for the simulation of highly intermittent hydrologic data is presented. Specifically, adaptations of the fractal-multifractal (FM) method and a Cantorian extension are advanced in order to... more
Application of a deterministic geometric approach for the simulation of highly intermittent hydrologic data is presented. Specifically, adaptations of the fractal-multifractal (FM) method and a Cantorian extension are advanced in order to simulate rainfall records measured at the daily scale and encompassing a water year. It is shown, using as case studies 2 years of rainfall sets gathered in Laikakota, Bolivia and Tinkham, Washington, USA, that the FM approach, relying on only at most 8 parameters, is capable of closely preserving either the whole record’s histogram (therefore including moments), the whole data’s Rényi entropy function and/or the maximum number of consecutive zero values present in the sets, resulting in suitable rainfall simulations, whose overall features and textures are similar to those of the observed sets. The study hence establishes the possibility of simulating highly intermittent sets in time in a deterministic and holistic way as a novel parsimonious methodology to supplement available stochastic frameworks.
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AbstractApplication of a deterministic geometric approach for the simulation of mildly intermittent hydrologic data, exhibiting a few peaks and displaying relatively slowly rising and falling limbs...
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California is a global leader in the agricultural sector and produces more than 400 types of commodities. The state produces over a third of the country’s vegetables and two-thirds of its fruits and nuts. Despite being highly productive,... more
California is a global leader in the agricultural sector and produces more than 400 types of commodities. The state produces over a third of the country’s vegetables and two-thirds of its fruits and nuts. Despite being highly productive, current and future climate change poses many challenges to the agricultural sector. This paper provides a summary of the current state of knowledge on historical and future trends in climate and their impacts on California agriculture. We present a synthesis of climate change impacts on California agriculture in the context of: (1) historic trends and projected changes in temperature, precipitation, snowpack, heat waves, drought, and flood events; and (2) consequent impacts on crop yields, chill hours, pests and diseases, and agricultural vulnerability to climate risks. Finally, we highlight important findings and directions for future research and implementation. The detailed review presented in this paper provides sufficient evidence that the clim...