Estimation of the economic value for the consumptive water use ecosystem service benefits of the Chyulu hills watershed, Kenya.

Abstract

The Chyulu Hills watershed ecosystem is a critical dryland water tower which supports large populations of people, livestock and wildlife in terms of water supply. The objectives of the study were to: - a) delineate the watershed ecosystem boundary based on the drainage network and locate the key water sources, b) undertake a comprehensive water use analysis to establish the consumptive beneficiaries and their consumption levels, and c) estimate the monetary value of the consumptive water use ecosystem service benefits. The watershed ecosystem boundary delineation was based on 30m Landsat imagery using ASTER Digital Elevation Model (DEM) and ArcGIS 10.3. Surface water sources were determined using secondary data and field assessment of springs and rivers while the groundwater sources were inventoried using available borehole records and household surveys of hand dug shallow wells. The water use analysis and monetization was based on both secondary and primary data derived from existing water use records and field interviews, respectively. The estimation of the monetary value was undertaken through the market price method (MPM) using the cost value. The results showed that the Chyulu Hills watershed ecosystem was more hydrologically productive in the north-eastern zone (Kiboko-Makindu-Kibwezi). The watershed ecosystem service beneficiaries were mainly the local domestic water users, small scale irrigators, large scale irrigators, livestock keepers, tourism operators, and conservationists. The average water consumer price was $0.03 for a 20 litre jerri can of water while the total monetary value for the consumptive water resources was estimated at Ksh46, 676,192 which translated to $466,862 per annum. The watershed ecosystem service value was highest in the eastern zone (Kibwezi) at approximately Ksh5,906($59)/km2 followed by the northern zone (Masimba-Kiboko-Makindu) at Ksh3,490($35)/km2 and Ksh2,579($26)/km2 in the southern zone (Kambu-Mtito Andei-Mzima Springs). The value was lowest in the western zone (Kajiado) at Ksh5.86 ($0.05)/km2. The total economic value (TEV) was much lower than the estimates for other similar dry land water towers in Kenya.