TOWARDS EFFECTIVE WATERSHED MANAGEMENT IN KENYA, A CASE STUDY OF MACHAKOS DISTRICT

Abstract

Water resources have diminished with time and space in many catchments due to poor management of the watersheds and over utilization of the resources. Water is a renewable though limited resource and therefore the need for it's long term planning is increasingly being felt. This is a study on water resources availability and utilization in Machakos district in Kenya so as to ascertain the extent of the deficit in the district whose potential has diminished so much resulting to food shortage and land degradation. The study area is the watershed of the upper Athi river basin in Machakos district. The district in the eastern part of the country covers an area of 6281 km2 most of which is semi arid. High and medium potential areas where rain-fed Agriculture is carried out is only 26% of the total area while 74% is rangeland with very limited irrigated or rain-fed agriculture. The land use and settlement patterns are based on Agro-ecological zones andare influenced by soil fertility and rainfall. The rocks underlying in the area are mainly sedimentary rocks made up of pre-Cambrian basement series known as the Mozambique belt system. Generally the soils lie in the range from sandy clay loam to sandy clay and are hydrologically classified in-group C and D. The agro-ecozones range from Zone 2 to Zone 6. The topography of the district is varied and rises from 700 m to 1700 m above the sea level with the highest point being Kilimambogo (Donyo Sabuk) at 2144 m. There are two distinct rainy seasons and the mean monthly temperatures range from 12° C to 250 C. The rainfall ranges from 700 mm on the plains to 1300 mm on the hills. The average annual evapotranspiration is about 1630.23 mm. As by 2002,the annual population growth rate was 1.7% and the population was 954,082 persons. It is expected that the population will be 970,440 by 2003, 1,092,606 by 2010 and 1,293,222 by 2020. The district depends upon rivers and streams, boreholes, springs and roof catchments for the sources of water. Water available from shallow well abstraction is 10.78 Mcm/year. There are 360 boreholes in the district but only 281 are currently operational with a total yield of 12.176 Mcm/year and Yatta canal provides 22.644 Mcm/year. Water used from Athi River (either by pumping or diverting) annually is 157.05 Mcm/year giving the total amount of water available in the district as 205.908 Mcm/year. iii The demand for human consumption is 35.754 Mcm/year; the industrial demand is 2.017 Mcm/year and the demand for livestock (Cattle, Shoats, Poultry, Pigs, Rabbits and Donkeys) is 4.835 Mcm/year. The crops grown are Maize, Sorghum, Millet, Pulses, Roots/Tuber crops, Fruit crops, Local market vegetables, Export market Vegetables and Industrial crops. The theoretical net irrigation water requirement (NIR) is 1,099.194 Mcm/year and the actual NIR is 252.635 Mcm/year. The total overall demand is 295.239 Mcm/year against an available amount of 205.908 • Mcm/year thus giving a deficit of 89.65 Mcm/year by 2002.The water deficit is expected to be _95.287 Mcm/year by 2003, 133.011 Mcm/year by 2010 and 195.239 Mcm/year by 2020 assuming the same trend of events. The rain-fed area is 323,968 ha and the irrigated area is 13034 ha. The cropping intensity is 167.7% and the irrigated cropping intensity is 10.7% and level if irrigation is 31.95%. An attempt has been made to evaluate the water resources in the study area in Kenya and analysis has been made to assess the level of water scarcity so as to quantify it. The average rainfall with 10-year return period has been estimated as 1110.00 mm. The Hydrological Soil Cover Complex method and the long term average water balance method by Thornwaite and Mather have been used to estimate the average annual runoff and the values 184.77 mm and 183.50 mm have been obtained respectively. Soil loss has been estimated using the Universal Soil Loss Equation. Present land treatments have been discussed and analyzed, both Agronomical and Mechanical works. Various methods have been recommended as suitable for the watershed. They include good farm management, companion crops, mulching, trash farming, contour farming, tied ridging or listing, cutoff drains, terraces, bunding, check dams, farm ponds, earth dams and agro-forestry. The total amount of water saved by all these measures is 446.221 Mcm/year (780.02 mm). Importance of participatory approach in watershed management has been discussed in detail pointing out the key areas, where and why it is required.