The potential for sand dams to increase the adaptive capacity of East African drylands to climate change

Abstract

Drylands are home to more than two billion people and are characterised by frequent, severe droughts. Such extreme events are expected to be exacerbated in the near future by climate change. A potentially simple and cost-effective mitigation measure against drought periods is sand dams. This little-known technology aims to promote subsoil rainwater storage to support dryland agroecosystems. To date, there is little long-term empirical analysis that tests the effectiveness of this approach during droughts. This study addresses this shortcoming by utilising multi-year satellite imagery to monitor the effect of droughts at sand dam locations. A time series of satellite images was analysed to compare vegetation at sand dam sites and control sites over selected periods of drought, using the normalised difference vegetation index. The results show that vegetation biomass was consistently and significantly higher at sand dam sites during periods of extended droughts. It is also shown that vegetation at sand dam sites recovers more quickly from drought. The observed findings corroborate modelling-based research which identified related impacts on ground water, land cover, and socio-economic indicators. Using past periods of drought as an analogue to future climate change conditions, this study indicates that sand dams have potential to increase adaptive capacity and resilience to climate change in drylands. It therefore can be concluded that sand dams enhance the resilience of marginal environments and increase the adaptive capacity of drylands. Sand dams can therefore be a promising adaptation response to the impacts of future climate change on drylands.

Dryland climate change: Recent progress and challenges

“…Based on this ratio, drylands can be further classified as hyperarid, arid, semiarid, and dry subhumid areas [ United Nations Convention to Combat Desertification (UNCCD) , ; Mortimore , ; Feng and Fu , ; Spinoni et al ., ]. Over drylands, precipitation is scarce and highly variable [ Middleton and Thomas , ; Vallejo et al ., ; Ryan and Elsner , ]. In contrast, PET, which represents the evaporative demand of the atmosphere, stays relatively high because of the high surface air temperature (SAT), low humidity, and abundant solar radiation over drylands [ Mortimore , ; Ji et al ., ].…”

Evaluation of sand-dam water quality and its suitability for domestic use in arid and semi-arid environments: A case study of Kitui-West Sub-County, Kenya

“…Among these methods, sand dams have become one of the most successful and reliable stormwater harvesting methods due to the simplicity in their construction, their ability to store water with minimum evaporation loss and protect it from direct surface contamination and from many water-borne diseases at a local scale and their ability to replenish adjacent shallow wells by raising water table, among others (Maddrell and Neal, 2012;Petersen and de Trincheria, 2015;Maddrell, 2016). They act as slow sand filters, purifying the water through seasonally accumulated sand layers in a natural and uncontrolled process and making it clean for drinking and domestic uses (Ryan and Elsner, 2016). In Makueni County as example, about 81% of the households relied on rivers/streams in which sand dam systems are dominant water harvesting structures (Kimani et al, 2015).…”

Learning from ancient water management: Archeology's role in modern‐day climate change adaptations

“…Sand dams are technologically quite simple and the costs are relatively low, yet the technique can increase water availability and considerably reduce vulnerability to water shortages, even in times of drought. 44, [46][47][48] In Africa sand dams have been constructed for several decades now, but especially the last decade has witnessed a real surge with their number now reaching into the thousands.…”