Abstract
In the Greater Serengeti-Mara ecosystem, with the Serengeti National Park (SNP) at its core, people and wildlife are strongly dependent on water supply that has a strong seasonal and inter-annual variability. The Mara River, the only perennial river in SNP, and a number of small streams originate from outside SNP before flowing through it. In those watersheds increasing grazing pressure from livestock, deforestation, irrigation and other land uses affect river flows in SNP that subsequently have impacts on wildlife. We quantified the changes since the 1970s of river discharge dynamics. We found that the baseflow recession period for the Mbalageti River has remained unchanged at 70 days, which is a natural system inside SNP. By contrast it has decreased from 100 days in the 1970s to 16 days at present for the Mara River, coinciding with increased commercial-scale irrigation in Kenya that extract Mara River water before it reaches SNP. This irrigation will result in zero flow in the river in SNP if the proposed dams in the river in Kenya are built. We observed high flash floods and prolonged periods of zero flows in streams draining livestock grazed watersheds, where severe major erosion prevails that results in gully formation. This eroded sediment is expected to silt and dry out the scattered dry season water holes in SNP, which are an important source of drinkable water for wildlife during the dry season. It appears likely that the future water supply of SNP is at risk, and this has major consequences for its people and wildlife. Ecohydrology-based solutions at the catchment scale are urgently needed to reduce catchment degradation while ensuring sustainable water provision.
Highlights
In the Greater Serengeti-Mara ecosystem, with the Serengeti National Park (SNP) at its core, people and wildlife are strongly dependent on water supply that has a strong seasonal and inter-annual variability
Our study does that by answering four hydrological questions of importance to the ecosystem, namely: (1) What are effects of livestock grazing in the Loliondo Game Controlled Area (LGCA; Fig. 1) outside SNP on the flow characteristics of small streams draining into SNP?; (2) What are the effects of fire inside SNP on the flow characteristics of small streams?; (3) Is the hydrology regime stable inside SNP?; (4) Is the Mara River likely to dry out in SNP in the future due to human activities in Kenya?
The streams originating from intensively cattle-grazed areas outside of SNP in Loliondo Game Controlled Area (LGCA) were mostly erosion gullies with intense erosion during high flows (Fig. 5d) and this gully formation propagated downstream in SNP (Fig. 5e)
Summary
In the Greater Serengeti-Mara ecosystem, with the Serengeti National Park (SNP) at its core, people and wildlife are strongly dependent on water supply that has a strong seasonal and inter-annual variability. Despite of the ecological importance of surface water, the availability of water in the ecosystem has not been monitored, nor has the threat to this water been quantified from the increased use of river water for irrigation, the increased use of fires, and the increased overgrazing by cattle in watersheds originating from upstream SNP but draining into SNP mainly through the Grumeti River If these flow dynamics are not quantified and monitored, their consequences for people and wildlife cannot be predicted and mitigated. We collected field data on the effects of land use regimes on the flow properties of streams draining small watersheds inside and outside SNP, and simultaneously we collected data on rainfall and the flows in the large rivers in SNP Using these data, we quantified the cause-and effects processes affecting these life supporting components of the ecosystem in SNP. Our study does that by answering four hydrological questions of importance to the ecosystem, namely: (1) What are effects of livestock grazing in the Loliondo Game Controlled Area (LGCA; Fig. 1) outside SNP on the flow characteristics of small streams draining into SNP?; (2) What are the effects of fire inside SNP on the flow characteristics of small streams?; (3) Is the hydrology regime stable inside SNP?; (4) Is the Mara River likely to dry out in SNP in the future due to human activities in Kenya?
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