Sand Dams in TSAVO

About Tsavo Trust

Tsavo Trust is an agile field based, action orientated, Kenyan not-for-profit conservation organisation working as a trusted partner of the National mandated wildlife management agency, the Kenya Wildlife Service (KWS) through a valid Memorandum of Understanding (MoU). Tsavo Trust provides core support to secure wildlife, habitat and key communities in Kenya’s vast Tsavo Conservation Area (TCA) in southern Kenya.

The TCA is vast and arid, comprising of Tsavo East (TENP), Tsavo West (TWNP) and Chyulu Hills National Parks – 22,000km2 (49% of Kenya’s Protected Area’s (PA’s)) plus dispersal areas into surrounding community land and ranches – another 20,000km2 to give a total of 42,000km2. The climatically hostile environment offers persistent limited availability of water to wildlife, which is worsened with the existing threats of climate change, habitat and vegetation loss, and human impacts on water systems adding to this fragile ecosystem.

The TCA provides habitat to rich biodiversity including Kenya’s largest single population of elephant (14,964 elephants – 2021 aerial census), 18% of Kenya’s black rhino population and approximately 4,314 Giraffe (2021 census figures). It is also home to the unique iconic “Big Tuskers” as well as to many other “high value” species including Hirola, Grevy’s Zebra, Wild Dog and much more.

Recent droughts in Tsavo, such as the 2017 drought; in which over 300 elephants in TENP died as a direct result of the drought, and the extended dry spell in 2019 (from March 2019 up until October 2019) and 2021 (May to November 2021 – 30 of 51 elephant carcasses located by Tsavo Trust in 2021 were confirmed to have died from drought) are real threats to the wildlife of Tsavo. The now seasonal rivers that once used to flow every year with regularity now flow only once every few years. Seven artificial waterholes, spread over an area of approximately 1100km became the only water source for wildlife during dry spells but the concentration of all wildlife around those artificial waterholes has resulted in a total destruction of the vegetation around them. The land around these water holes is so over-exploited that many hundreds of animals die around them, especially the very young, old and the weak, because the distance to food and making it back to the waterholes is too far.

In an effort to mitigate the effects of diminishing water sources for wildlife, Tsavo Trust with support from Disney / Wildlife Conservation Society (WCS) conducted a Sand Dam Construction – Pilot Phase in TENP 2019/20 and a Phase 2 and 3 Sand Dam Construction in TWNP 2020/21/22 were 1 and 4 sand dams were constructed within the PA to benefit wildlife respectively. Following the December rains in 2021 all 5 sand dams were filled with water, providing water for wildlife for at least 2 months after the rains subsided – this duration of water storage will grow with time as the sand dam fills with sand, but shows a
good indication that these dams are working. Moreover, vegetation restores around those small oases (restoring also wildlife carrying capacity) and allow elephants and other wildlife to hang around a while longer. The sand dams therewith promote spreading of wildlife and reduces pressure from excessive concentration of wildlife around the artificial water holes. Tsavo Trust has recently raised funds to construct a further 2 sand dams in the TENP Intensive Protection Zone which will start in October 2022.
Tsavo Trust and partners (Kenya Wildlife Service, African Sand Dam Foundation and Sand Dams Worldwide) have developed a 5 year plan to roll out five sand dams per year for the next five years – completing 25 after 5 years. 8 sand dams have been constructed under this plan to date. This will very significantly upgrade natural water source catchment for wildlife in appropriate areas in Tsavo East and Tsavo West National Parks. The benefits are clearly there to see at the sand dams that we have already constructed, and we are very excited about this development.

Sand Dam Concept

A Sand Dam is essentially a reinforced stone wall build across a seasonal sandy riverbed, generally on top of a stone bedrock. Water behind the sand dam raises the water table and is held within the collected sand that in turn acts as a sponge and holds water for long dry periods with no loss through evaporation. The surrounding habitat of the sand dam significantly improves and creates better conditions for vegetation growth.

The sand dam concept is a well-known, tried and tested method of providing small but consistent amounts of water through a seepage system on the downside of the dam wall. This is ideal in arid areas and it does not create the “desertification effect” that is often associated with sinking of bore holes in PA’s where elephant numbers are high. Upstream from the dam wall is filled with river sand when the seasonal riverbed flows during the rainy season. This sand filled dam acts as the sponge to hold significant water supplies that are then drip fed to wildlife.

Sand dams have been used to great effect in dry arid regions for both humans and livestock and now through this project there is no reason why wildlife cannot reap the same benefits within wildlife conservation areas. Water supply and distribution for wildlife in the Tsavo’s has always been a huge challenge to address, particularly during the dry season due to erratic rain patterns and the sandy soils that cannot hold water for extended periods, unless they are well captured within water courses, such as through the sand dam idea. The sand dam plan could well be one answer to this problem, by construction several well designed and distributed sand dams over the coming years within the TCA.

Some direct benefits of Sand Dams are:

They hold millions of litres of water
They are hugely sustainable
They are replenished with every rainfall
They recharge the groundwater (water table)
They last for decades
They support surrounding vegetation growth, highly important for all wildlife
They can help to reduce erosion
They require little or no maintenance
They demagnetize wildlife away from other focal water holes and with this reduce the spread of desertification around those points

Construction costs for each Sand Dam vary considerably depending on the valley size, distance from water, accessible roads etc. We have approximated US$35,000 to $40,000 per sand dam. This includes aerial survey to locate suitable sites, ground visits with partners to ascertain suitable locations, sand dam designs, EIA and NEMA licensing, purchase of materials, labor and construction.

The EIA / NEMA licensing usually takes the longest but the construction process can be relatively quick lasting between 6 weeks and 2 months for the construction of one dam.

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