Abstract: Competing commercial demands on water resources need to be balanced as the world’s population rises. Generally, groundwater is raised by subsurface dams. In this paper, the geographic information system (GIS) software and a decision-making method were applied. As the first step, the limitations that affect the establishment of the subsurface dam were identified using eliminating criteria by the Boolean logic. Regarding the second step, the most appropriate axis was determined for subsurface dam construction in each of the limits. The analytical hierarchy process (AHP) was applied according to the evaluation criteria in this study. The aim of using AHP was to weigh and prioritize the criteria of the groundwater dam for recognizing appropriate sites. Among various places and regarding the subsurface dam construction, AHP was conducted using a hierarchy process for finding the most suitable sites in the third stage of the decision-making method. Finally, among the ten appropriate sites, cross comparison was drawn by using Decision Expert (DEX), Evaluation based on Distance from Average Solution (EDAS), and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). Compared together (as a process of decision-making), DEX, TOPSIS, and EDAS methods assisted in ranking the most appropriate sites in the final step of subsurface dam pre-selection. A and C axes obtained scores between 1 and 2, among 10 axes according to the numerically ranked locations. Regarding the water shortage issue and better management of the underground water at certain levels, the findings of this study could be useful for the residents of Kajbid-Balaqly Watershed in the dry season. Further, water managers can use the above-mentioned methods for their decisions regarding the proper subsurface dam establishment.

Abstract: Rainwater harvesting (RWH) systems have been developed to compensate for shortage in the water supply worldwide. Such systems are not very common in arid areas, particularly in the Gulf Region, due to the scarcity of rainfall and their reduced efficiency in covering water demand and reducing water consumption rates. In spite of this, RWH systems have the potential to reduce urban flood risks, particularly in densely populated areas. This study aimed to assess the potential use of RWH systems as urban flood mitigation measures in arid areas. Their utility in the retention of stormwater runoff and the reduction of water depth and extent were evaluated. The study was conducted in a residential area in Bahrain that experienced waterlogging after heavy rainfall events. The water demand patterns of housing units were analyzed, and the daily water balance for RWH tanks was evaluated. The effect of the implementation of RWH systems on the flood volume was evaluated with a two-dimensional hydrodynamic model. Flood simulations were conducted in several rainfall scenarios with different probabilities of occurrence. The results showed significant reductions in the flood depth and flood extent, but these effects were highly dependent on the rainfall intensity of the event. RWH systems are effective flood mitigation measures, particularly in urban arid regions short of proper stormwater control infrastructure, and they enhance the resilience of the built environment to urban floods.

Abstract: Travel time distributions (TTDs) provide an effective way to describe the transport and mixing processes of water parcels in a subsurface hydrological system. A major challenge in characterizing catchment TTD is quantifying the travel times in deep groundwater and its contribution to the streamflow TTD. Here, we develop and test a novel modeling framework for an integrated assessment of catchment scale TTDs through explicit representation of 3D-groundwater dynamics. The proposed framework is based on the linkage between a flux tracking scheme with the surface hydrologic model (mHM) for the soil-water compartment and a particle tracking scheme with the 3D-groundwater model OpenGeoSys (OGS) for the groundwater compartment. This linkage provides us with the ability to simulate the spatial and temporal dynamics of TTDs in these different hydrological compartments from grid scale to regional scale. We apply this framework in the Nägelstedt catchment in central Germany. Simulation results reveal that both shape and scale of grid-scale groundwater TTDs are spatially heterogeneous, which are strongly dependent on the topography and aquifer structure. The component-wise analysis of catchment TTD shows a time-dependent sensitivity of transport processes in soil zone and groundwater to driving meteorological forcing. Catchment TTD exhibits a power-law shape and fractal behavior. The predictive uncertainty in catchment mean travel time is dominated by the uncertainty in the deep groundwater rather than that in the soil zone. Catchment mean travel time is severely biased by a marginal error in groundwater characterization. Accordingly, we recommend to use multiple summary statistics to minimize the predictive uncertainty introduced by the tailing behavior of catchment TTD.