Hydrograph Separation

The hydrograph separation of the Amazon river was performed using three different methodologies. Were applied isotopic, filter-separation, and mixing methods to estimate the contributions of the surface runoff (event water) and baseflow (pre-event water) components to the total river flow, during the 1973–1974 hydrological years. The importance of the baseflow contribution, mainly during the peak discharge, suggesting that the groundwater plays a much more active and important role in the storm dynamics, was verified. Similar results were obtained for all the methods used, and the applicability of each one was discussed in detail. For the Amazon river basin, the average contribution of the baseflow was 56% of the total river flow, at peak discharge. The average surface runoff contribution, which represents the water capable of mechanical erosion in drainage basins, expressed in terms of the surface runoff coefficient (Kr), was 31.9%, while the mean contribution of the baseflow, expressed by the baseflow coefficient (Kb), was 68.1%.

Karst aquifers provide 25% of the overall drinking water resources to the world's population and sustain aquatic life in most fluvial systems, providing several ecological services to human beings, although, because of their complex links between surface and groundwater, turn out to be very vulnerable to contamination and pollution. This paper describes the preliminary findings from Radon-222 activity concentration measurement data collected in streamflow and instream springs during monthly field campaigns, performed from September 2007 to December 2008, in a typical Mediterranean karst river: the Bussento river (Campania region, Southern Italy). The general aim is to investigate the complex interactions and exchanges between streamflow and groundwater, at scales that are imperceptible to standard hydrological and hydraulic analyses. In fact, the study area is located inside the Cilento and Vallo di Diano National Park and, therefore, the management of its relevant water resources requires not only groundwater protection for domestic drinking use, but also riverine wildlife preservation and coastal water quality maintenance. As a support for hydro-geomorphological and hydrological modelling for planning tasks, in application of the European Water Framework Directive (EWFD), a Bussento River Monitoring System (BRMS) has been built, at basin, segment and reach scale. Experimental data about 222Rn concentrations, in addition to physical-chemical and streamflow rate, have been acquired and managed from BRMS selected stations, sampling the streamflow and inflow spring waters by means of the Radon-in-Air analyzer, RAD7, together with the Radon-in-water accessories, Radon Water Probe and RAD7H2O (DURRIDGE Co. Inc.), for continuous and batch sampling measurements, respectively. During preliminary surveys, appropriate sampling procedures and measurement protocols have been tested, taking into account the different local hydrogeological and hydrological situations occurring along the Bussento river basin. At segment scale, data elaborations from the Bussento mid-lower segment provide the location and downstream influences of the groundwater inflows from river banks and bed, also in absence of valuable streamflow discharge increments. At river reach scale, more detailed data enable to improve a preliminary model about the 222Rn degassing rate, related to the hydro-geomorphological Rosgen stream type and provide a first contribution to surficial-groundwater seasonal hydrograph separation. Finally, the analysis of the seasonal data trends from karst springs confirms the hydrogeological conceptual model, highlighting the complex behaviour of a multilevel groundwater circuits, the uppermost in caves, the mid in conduits and the lowermost in fracture network, corresponding to the differentiated recharge types in the fluvial-karst hydro-geomorphological system.

The δ 18 O of rainfall shows large variations (−12.6 to +2.1‰) related to different air-masses. There is no correlation between δ 18 O values in rainfall, temperature, and rainfall amount. Local meteoric water lines for rainfall and throughfall suggested that evaporation was minimal. ...

Objectives and Background
Extraction of the base flow index (BFI) has been one of the most important issues in hydrology and plays a key role in the optimal water resources management .Development of the base flow analysis from the hydrograph has a long-term history which date back to the theoretical and experimental research of Horton, (5). In this regard, numerous and useful literature review is presented to show progress, (14, 25, 27). Different methods of hydrograph separation were examined using correlation analysis by Nathan and McMahon (1990).they suggested a simple one parameter digital filter with 0.925 coefficients (18). Different graphical, digital and tracing methods were studied in the catchments of the lowlands of the Netherlands by Gonzalez et al (2009). Results showed that Eckhart algorithm is a good method in the lowlands (12). Literature review showed that In relation to the comparison of different base flow separation methods on the basis of different climates, enough research has not been done in the country. The aim of this study is investigation of different base flow separation methods using flow duration curve indices In order to select the most appropriate method.

Materials and methods
In this research, the base flow and BFI were extracted using daily flows of twenty gauging station located in the Khazar region. Seven algorithms were selected, four based on recursive digital filter (One-parameter algorithm, Boughton two parameter algorithm, BFLOW algorithm, Chapman algorithm) and the others on simple smoothing (Local minimum, Fixed interval, Sliding interval).Filter coefficients selected in the range required for each method according to the best response to changes in the coefficients and using the graphical display of Hydro Office software. Flow duration curve of all the stations traced and their indices were extracted. Results were evaluated using different statistical methods (Mean absolute error, Standard deviation, and Standard error of estimate, Coefficient of determination and Correlation Matrix) with respect to flow duration indices. Since the parameters extracted from the flow duration curve is calculated using the measured and observational data and this index known as an indicator of the groundwater contribution to the steam flow. Therefore, as representative of the actual flow were used for comparison of hydrograph separation models.

Results
The results showed that the average annual of BFI, fluctuate between 0.56 and 0.91, which related to one parameter recursive digital filter and B-Flow algorithms. This value represents a high ground water contribution in stream flow in the study area. Correlation matrix between different set of BFI values and flow duration curve indices showed high value of coefficient of determination between B-Flow method and Q90/Q50 and the lowest were identified between Chapman and Fixed intervals. Comparison of Standard division of different methods showed that B-FLOW has the lowest standard deviation. In addition, this method has the highest correlation with the flow duration curve index. On the basis of these two criteria’s, B-Flow recursive digital filter compared to other, was diagnosed as a better option. According to the Mean absolute error, and Standard error of estimate, one parameter method had the best estimate.

Conclusion
The overall conclusion obtained using different statistical tests were found to yield suitable estimation of base flow index by one parameter algorithm because of low Mean absolute error, the lowest Standard error of estimate and 0.71 coefficient of determination with flow duration curve index. This method in the absence of tracing methods, were diagnosed as the most appropriate method in the study area.

By 1994, an estimated 1.8 million hectares of cleared land in Western Australia was affected by secondary dryland salinity to some extent. The area affected is likely to double in the coming 20 years. The cause of this salinity is excessive recharge under traditional agriculture, leading to rising groundwater levels. Monitoring changes in groundwater levels is helpful in indicating the degree of threat to agricultural land and public assets. Many researchers have studied groundwater level rises and attempted to explain them ...

Hydrograph separation method reported in Mei & Anagnostou (2015) includes two aspects: baseflow separation and event identification. The baseflow separation method, namely filtered revised constant k (FRCK) method, is a hybrid-method of the revised constant k (RCK) and recursive digital filter (RDF); it splits the streamflow record into baseflow and event flow component. The event identification method is called characteristic point method (CPM); it extracts rainfall-runoff events from long records of streamflow and basin- average rainfall time series, based on the time series characteristics. More information about this method can be found in the "CPM User Manual_4.3.2017.pdf" document.
The above hydrograph separation methods are contained in six Matlab codes: two for the baseflow separation section and four codes for the event identification. The manuscript provides detailed explanation on the uses, inputs and outputs of these Matlab codes. It is accompanied by a demo Matlab code, illustrating an example basin.
Matlab code can be downloaded from http://ucwater.engr.uconn.edu/models-data/ or https://www.researchgate.net/profile/Yiwen_Mei/publication/316148287_User_Manual_of_the_Characteristic_Point_Method_for_Automatic_Hydrograph_Separation/data/5936ba83458515969b900991/CPM-662017.zip.

Runoff generation in a Mediterranean carbonate rock environment—the Judaean Mountains, West Bank and Israel—was studied by a 2 day sprinkling experiment on an 18 × 10 m2 plot. During the first day, three spells of 24·1 mm h−1 (12·3 mm), 27·8 mm h−1 (12·3 mm) and 14·4 mm h−1 (12·5 mm) were applied, almost saturating the runoff plot. On the second day, 20 h later, two spells of 18·7 mm h−1 (34·3 mm) and 35·2 mm h−1 (25·4 mm) followed. Surface runoff was a combination of infiltration excess runoff from rocky portions of the plot and saturation excess runoff from areas covered by soil. Soil saturation was accelerated by lateral runoff from adjacent rocky areas. Once the plot was saturated, 80–90% of the applied rainfall became surface runoff. Significantly different concentrations of chloride, sulphate, and nitrate ions in the sprinkled water on two successive days served as tracers. During the second day a two-component hydrograph separation pointed to the importance of shallow reservoirs playing active parts in runoff generation. About 14% of the flow collected during the second day originated from water applied during the first day. During the second day of sprinkling, both water sources obviously mixed in saturated soil reservoirs and contributed in variable percentages to surface flow. It is hypothesized that, at least during high-magnitude rainfall, the steep rocky slopes investigated might be regarded as flood-generating zones rather than areas of pronounced recharge into the underlying Yarkon–Taninim aquifer. Copyright © 2003 John Wiley & Sons, Ltd.

... Markus C. Casper a , Corresponding Author Contact Information , E-mail The Corresponding Author , Holger N. Volkmann a , Guido Waldenmeyer b , Erich J ... of organic carbon play an important role in the ecosystem, driven by water as the transport medium (McDowell and Wood ...

Soil solution and free-flowing soilwater were sampled at various depths for 3 years in a plot of holm oak (Quercus ilex L.) in the Montseny mountains (NE Spain). The soil solution retained at −65M kPa in the mineral soil at depths of 20 and 40 cm had a different chemistry from that of throughflow under the humic layer (H-layer throughflow)