Impacts of land‐use/cover changes on the hydrology of the transboundary Mara River, Kenya/Tanzania

Abstract

The Mara River is the lifeline of the transboundary Mara basin across Kenya and Tanzania. The basin is considered one of the more serene subcatchments of the Lake Victoria Basin and ultimately the Nile Basin, and traverses the famous Maasai Mara and Serengeti National Parks. The basin also contains forests, large-scale farms, smallholder farms, pastoral grazing lands, as well as hunter gatherers and fishers. There is growing concern, however, regarding land degradation in the basin, particularly deforestation in the headwaters, that is affecting the natural resource base and the river flows. Accurate scientific data are required to advise policy, and to plan appropriate mitigation measures. This study utilizes remote sensing and geographical information system (GIS) tools, and hydrological and ground-truth studies to determine the magnitude of the land-use/cover changes in the Mara River Basin, and the effects of these changes on the river flows over the last 30 years. The study results indicate that land-use/cover changes have occurred. In 1973, for example, rangelands (savannah, grasslands and shrublands) covered 10 989 km 2 (79%) of the total basin area. The rangelands had been reduced to 7245 km 2 (52%) by 2000, however, while the forest areas were reduced by 32% over the same period. These changes have been attributed to the encroachment of agriculture, which has more than doubled (203%) its land area over the same period. The hydrology of the Mara River also has changed, with sharp increases in flood peak flows by 7%, and an earlier occurrence of these peaks by 4 days between 1973 and 2000. There is evidence of increased soil erosion in the upper catchments, with silt build-up in the downstream floodplains. This has caused the Mara wetland to expand by 387%, adversely affecting riparian agriculture. There is need for urgent action to stem the land degradation of the Mara River Basin, including planning and implementing appropriate mitigation measures.

Changes in land cover, rainfall and stream flow in Upper Gilgel Abbay catchment, Blue Nile basin – Ethiopia

“…Increases of high flow discharges are expected in areas where agricultural land has largely increased by deforestation and in case of land degradation (e.g. Mati et al, 2008;Costa et al, 2003). The decrease of low flows in this work is also described in Kashaigili (2008) and Bewket and Sterk (2005) but is not described in Zhang and Schilling (2006) and Siriwardena et al (2006).…”

“…Bewket and Sterk, 2005;Costa et al, 2003;Siriwardena et al, 2006), an increase in high flow (e.g. Mati et al, 2008;Costa et al, 2003) and an increase in base flow (e.g. Zhang and Schilling, 2006).…”

Assessing the Land Use/Cover Dynamics and its Impact on the Low Flow of Gumara Watershed, Upper Blue Nile Basin, Ethiopia

“…After the model, has been calibrated, the consistency of the model parameter values has also been verified by using four-year (1992)(1993)(1994)(1995) climate data and 1986 land use/cover data [11].…”

Hippopotamus and livestock grazing: influences on riparian vegetation and facilitation of other herbivores in the Mara Region of Kenya

“…Marked declines in herbivore numbers in the Mara have been attributed to their progressive exclusion from the pastoral ranches by land-use changes, including expanding Landscape Ecol Eng (2013) 9:47-58 49 mechanized and subsistence agriculture and settlements, which have affected over 8% of the Mara and caused landcover changes in at least 36% of the pastoral ranches adjoining the MMNR (Homewood et al 2001;Lamprey and Reid 2004;Mati et al 2008). These changes have intensified competition between livestock and wild herbivores in the pastoral ranches of the Mara.…”

“…The Mara River is about 396 km long and its flow through the MMNR and SNP sustains a wide variety of abundant herbivore species, 10 of which form the main focus of this study, and include the hippopotamus (Hippopotamus amphibious, Linnaeus 1758), wildebeest (Connochaetes taurinus Burchell, 1823), Burchell's zebra (Equus burchelli Gray 1824), the African buffalo (Syncerus caffer, Sparrman 1779), topi (Damaliscus korrigum, Ogilby 1837), Coke's hartebeest (Alcelaphus buselaphus, Gunther 1884), Grant's gazelle (Gazella granti, Brooke 1872), Thomson's gazelle (Gazella thomsoni, Günther 1884), warthog (Phacochoerus aethiopicus, Gmelin 1788) and impala (Aepyceros melampus, Lichtenstein 1812). Populations of these herbivore species face water-related constraints in the Mara in the dry season, including increasing water shortages and declining water quality linked to expanding irrigated cultivation, unregulated water extractions and deforestation of the Mau Forest catchments of the Mara River (Mati et al 2008).…”