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Tamagnone, P., Comino, E., & Rosso, M. (2020). Rainwater harvesting techniques as an adaptation strategy for flood mitigation. Journal of Hydrology, 586, 124880.
Abstract: The development of adaptation and mitigation strategies to tackle anthropic and climate changes impacts is becoming a priority in drought-prone areas. This study examines the capabilities of indigenous rainwater harvesting techniques (RWHT) to be used as a viable solution for flood mitigation. The study analyses the hydraulic performance of the most used micro-catchment RWHT in sub-Saharan regions, in terms of flow peak reduction (FPR) and volume reduction (VR) at the field and basin scale. Parametrized hyetographs were built to replicate the extreme precipitations that strike Sahelian countries during rainy seasons. 2D hydrodynamic simulations showed that half-moons placed with a staggered configuration (S-HM) have the best performances in reducing runoff. At the field scale, S-HM showed a remarkable FPR of 77% and a VR of 70% in case of extreme rainfall. Instead at the basin scale, in which only 5% of the surface was treated, 13% and 8% respectively for FPR and VR were obtained. In addition, the reduction of the runoff coefficient (Rc) between the different configuration was analyzed. The study critically evaluates hydraulic performances of the different techniques and shows how pitting practices cannot guarantee high performance in case of extreme precipitations. These results will enrich the knowledge of the hydraulic behavior of RWHT; aspect marginally investigated in the scientific literature. Moreover, this study presents the first scientific application of HEC-RAS as a rainfall-runoff model. Despite some limitations, this model has the effective feature of using very high-resolution topography as input for hydraulic simulations. The results presented in this study should encourage stakeholders to upscale the use of RWHT in order to lessen the flood hazard and land degradation that oppresses arid and semi-arid areas.
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Akter, A., Tanim, A. H., & Islam, M. K. (2020). Possibilities of urban flood reduction through distributed-scale rainwater harvesting. Water Science and Engineering, 13(2), 95–105.
Abstract: Urban flooding in Chittagong City usually occurs during the monsoon season and a rainwater harvesting (RWH) system can be used as a remedial measure. This study examines the feasibility of rain barrel RWH system at a distributed scale within an urbanized area located in the northwestern part of Chittagong City that experiences flash flooding on a regular basis. For flood modeling, the storm water management model (SWMM) was employed with rain barrel low-impact development (LID) as a flood reduction measure. The Hydrologic Engineering Center’s River Analysis System (HEC-RAS) inundation model was coupled with SWMM to observe the detailed and spatial extent of flood reduction. Compared to SWMM simulated floods, the simulated inundation depth using remote sensing data and the HEC-RAS showed a reasonable match, i.e., the correlation coefficients were found to be 0.70 and 0.98, respectively. Finally, using LID, i.e., RWH, a reduction of 28.66% could be achieved for reducing flood extent. Moreover, the study showed that 10%–60% imperviousness of the subcatchment area can yield a monthly RWH potential of 0.04–0.45 m3 from a square meter of rooftop area. The model can be used for necessary decision making for flood reduction and to establish a distributed RWH system in the study area.
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Naghedifar, S. M., Ziaei, A. N., Naghedifar, S. A., & Ansari, H. (2020). A new model for simulation of collection and conveyance sections of Qanat. Journal of Hydrology, 590, 125218.
Abstract: In this paper, a new numerical model has been developed for simulation of Qanat-aquifer system. This model employs quasi-3D mixed-form of Richards’ equation and 1D fully-hydrodynamic form of Saint-Venant equations to simulate subsurface and overland flow, respectively. In order to handle non-orthogonal grids, subsurface flow module benefits from coordinate transformation technique. Using the above-mentioned governing equations, the presented model is able to simulate water flow inside both collection and conveyance sections of the gallery as well as dynamics of groundwater and vadose zone from impermeable bed rock to the soil-air interface. Since measured data corresponding to the hydraulics of Qanats is scarce, the overland and subsurface modules have been validated with analytical, numerical and experimental benchmarks in the literature. Subsequently, the model was employed to simulate ten different hypothetical aquifer-Qanat systems with different properties including the depth of groundwater aquifer, roughness of the gallery and saturated hydraulic conductivity of the gallery-aquifer boundary and the influence of each the parameters was monitored on the outflow rate at the appearance point of each Qanat. Furthermore, the advance of water inside two initially dry galleries were simulated at different time levels up to steady state. Eventually, the streamlines have been shown at the steady state for two Qanat-aquifer systems. Although, the presented study sheds light on some aspects of Qanat-aquifer hydraulics, the validation of the presented model with in-lab or on-field data remains ongoing for the future researches.
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Sedghi, M. M., & Zhan, H. (2020). Semi-analytical solutions of discharge variation of a qanat in an unconfined aquifer subjected to general areal recharge and nearby pumping well discharge. Journal of Hydrology, 584, 124691.
Abstract: Qanat is a type of drain that extract water from aquifers by gravity. Significant amount of fresh water used in Middle East and other parts of the world are supplied by qanats. Despite their importance, discharge variation of these type of wells received almost no attention. The aim of this research is to obtain a Laplace domain solution of discharge variation of a qanat installed in an anisotropic unconfined aquifer subjected to arbitrary areal recharge and nearby pumping well(s) discharge. A new semi-analytical solution of drawdown is obtained first to implement the effects of arbitrary areal recharge and nearby pumping well(s) using the principle of superposition. Then, the discharge variation solution of the qanat is obtained from the drawdown solution. To establish a constant-head boundary condition at the qanat periphery, the qanat is discretized into several segments. The results of this study are presented in dimensionless discharge-dimensionless time curves. The effects of hydraulic as well as geometric parameters on the discharge variation of the qanat due to arbitrary areal recharge, falling of water table from its initial position and discharge of nearby wells are explored. We also investigate the influences of distance and screen depth and location of the nearby well on the discharge variation of the qanat. The results of this study can be utilized for multiple purposes: 1) to predict discharge of qanat in response to rainfall and nearby pumping well(s); 2) to estimate the aquifer parameters using hydrograph of the qanat; 3) to determine optimal location and pumping pattern of the nearby wells to minimize their influences on the discharge of the qanat; 4) to calculate water budget of aquifers drained by a qanat. The equation presented in this work can also be used to estimate discharge of a horizontal drain installed in cropland subjected to arbitrary irrigation pattern.
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Konapala, G., Mishra, A. K., Wada, Y., & Mann, M. E. (2020). Climate change will affect global water availability through compounding changes in seasonal precipitation and evaporation. Nature Communications, 11(1), 3044.
Abstract: Both seasonal and annual mean precipitation and evaporation influence patterns of water availability impacting society and ecosystems. Existing global climate studies rarely consider such patterns from non-parametric statistical standpoint. Here, we employ a non-parametric analysis framework to analyze seasonal hydroclimatic regimes by classifying global land regions into nine regimes using late 20th century precipitation means and seasonality. These regimes are used to assess implications for water availability due to concomitant changes in mean and seasonal precipitation and evaporation changes using CMIP5 model future climate projections. Out of 9 regimes, 4 show increased precipitation variation, while 5 show decreased evaporation variation coupled with increasing mean precipitation and evaporation. Increases in projected seasonal precipitation variation in already highly variable precipitation regimes gives rise to a pattern of “seasonally variable regimes becoming more variable”. Regimes with low seasonality in precipitation, instead, experience increased wet season precipitation.
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Mahindawansha, A., Külls, C., Kraft, P., & Breuer, L. (2020). Investigating unproductive water losses from irrigated agricultural crops in the humid tropics through analyses of stable isotopes of water. Hydrology and Earth System Sciences, 24(7), 3627–3642.
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