Study of hydrological processe associated with groundwater aquifer fed by the monitors, chemical and isotopic ,case study: watershed hashtgerd

In this study, measured soil water' groundwater and rainfall chemical and isotope signatures and long_term precipitation profiles will be used to provide temporal estimates of recharge, and runoff and to consider the wider implications for water resource development in similar regions. Applying the tracer mass balance technique to soil water tracer profiles improves the boundary conditions associated with the long_term mean recharge rate. Temporal estimates of runoff are calculated from precipitation and soil water. Next. these estimates and measured precipitation are used as inputs in an unsaturated groundwater Model to estimate temporal recharge' which is subsequently compared to the long_term mean recharge rate calculated from the tracer profiles. Finally, the runoff components of the model are scaled such that the modeled recharge rate is similar to the long_term mean recharge rate. This method improves the tracer mass balance information for assumed changes in future' which up to now only provides long_ term mean recharge. Additionally' the method allows initial estimates of runoff to be scaled such that the resulting estimates of runoff are consistent with both tracer mass balance and water mass balance. Although direct methods to measure recharge and runoff are attractive' they are not always reasonable due to the expense of collecting data over long time periods. In contrast, this method obtains its required input from basic meteorological data and soil cores collected at a single point in time. As part of a comprehensive research project to quantify the various facets of river-aquifer interaction, namely to describe the hydro geological situation' high resolution 2D geoelectric measurements will be adopted and used in the study catchment. The resistivity measurements were supplemented by laboratory measurements on soil and a few groundwater samples. This allowed computing the formation factor K independently. Additionally using the physically based variably saturated flow model HYDRUS, wintertime observations will be modeled to determine the recharge of soil moisture at different depth intervals in the study area. Two approaches will be carried out to estimate the soil model parameters. The first will be to use basic soils data from detailed profile descriptions in conjunction with pedotransfer functions. The second parameter estimation strategy will be using automatic parameter search algorithm to find the optimal soil parameters that minimize the error between the model-computed volumetric water content and observations. In the next part of the study the results obtained by geoelecteric will be compared to the first and second part of the analysis.