Assessing the Impact of Land Cover, Soil, and Climate on the Storage Potential of Dryland Sand Dams

Abstract

Sand dams, a water-harvesting structure employed by rural communities in drylands have an inconsistent record of effectiveness. While many sand dams are highly functioning, improper siting, siltation, seepage, and high rates of evaporation from shallow sand reservoirs inhibit the water storage capacity of some sand dams. This study examines large-scale drivers of sand dam storage potential through analysis of an integrated surface and subsurface flow model. Multiple simulations were run, and comparative simulation analyses consider the effect of geomorphological factors, intraseasonal rainfall variability, and future climate conditions on sand dam performance criteria. The analyses revealed that a watershed highly cultivated with low water crops actually reduces evapotranspiration below that of natural vegetation and supports higher groundwater recharge. Additionally, intraseasonal variation and volume of rainfall impact sand dam performance less than the prevailing pattern and duration of dry and rainy seasons. Sand dams constructed in watersheds with sandier soils may experience greater connectivity with the stream margins and thus provide additional groundwater recharge. Lastly, climate change may improve some conditions desirable for sand dam performance, such as extending the duration of the rainy season and reducing overall evapotranspiration. However, the interactions between the expected climate change conditions and other geomorphological factors may result in a net decline in sand dam performance. The results of this study may help identify watersheds that are likely to support a sand dam with high potential for capturing and storing water throughout the dry season.

Dam Site Characterization Based on Land Use and Land Cover Changes in Urban Catchments. A Case of the Msimbazi Catchment in Dar es Salaam, Tanzania

“…The direction of the sharpest slope, or largest drop, from each cell, determines the flow direction. It is calculated using the formula in Eq (1).…”

“…Changes in the land surface cover have a significant likelihood of impacting evapotranspiration rates and surface runoff, and they may also have an impact on infiltration and stream discharge. To be more precise, land cover influences how quickly a sand dam reaches its storage capacity as well as how quickly that storage is used up [1]. Therefore, if a dam location site has been poorly selected, it can have several negative effects, including the risk of erosion leading to mudslides and landslides, the potential for receiving either high or low flows that were not anticipated during the design process (potential failure), as well as be linked to significant negative economic benefits.…”

An Alternative Approach for Improving Prediction of Integrated Hydrologic‐Hydraulic Models by Assessing the Impact of Intrinsic Spatial Scales

“…Examples of integrated models include ParFlow (Kollet & Maxwell, 2006), Interconnected Channel and Pond Routing (ICPR; Streamline Technologies, 2018), GSSHA (Downer & Ogden, 2006), MIKE‐SHE (Abbott et al., 1986), and HGS (Aquanty Inc., 2013). In recent years, integrated models have been applied for several applications, including but not limited to, agriculture sustainability (Schoups et al., 2005), runoff generation (Kollet & Maxwell, 2006; VanderKwaak & Loague, 2001), water harvesting (Eisma et al., 2021), stream‐aquifer exchanges (Gunduz & Aral, 2005), energy balance (Jefferson et al., 2015), and short‐term forecasting and inundation mapping of natural hazards (Chen et al., 2017; Saksena & Merwade, 2017; Saksena et al., 2019, 2020). However, the use of integrated models is still in a nascent stage in large‐scale riverine modeling (Jones et al., 2008; Maxwell et al., 2014; Rassam et al., 2013; Saksena et al., 2019).…”