Abstract:
Mt. Kenya serves as a natural water tower within a savanna-dominated environment. The semi-arid and arid lowlands northwest of the mountain are highly dependent on the perennial rivers that flow from it. Hence, pressures on rivers in the upper reaches put a direct strain on down-stream users. Major water users located in the foot-zone northwest of Mt. Kenya include the commercial horticultural companies, which began establishing themselves in the area in the 1990s. These enterprises produce vegetables and flowers for export markets, operating on perennial irrigation schemes. With increased water demand, the potential for conflicts over water allocation grows, demanding careful management and negotiation of river water use during dry season. Therefore, the present study analyzes the development of the commercial horticulture sector northwest of Mt. Kenya and determines its impact on river water resources of various tributaries of the Ewaso Ng’iro in order to provide a better understanding of this actor-category. A previous master thesis written by Roland Schuler (2004) concerned itself with this same topic, covering the period from the sector’s foundations in 1991 until 2003. This follow-up study covers the subsequent decade from 2003 to 2013. Conducting expert-interviews with the concerned horticulturist enabled the analysis of four main research foci: the inventory and structure of the commercial horticulture sector; the factors of change influencing its development; the sector’s impact on river water resources; and its socioeconomic influence on the region. The study shows a continuous growth of the commercial horticulture sector: the number of farms operating in the study area increased from 28 to 35 covering a total area of 1385 hectares (ha) in 2013 compared to 1085 ha in 2003. Moreover, there has been a major shift from vegetable crop production to floriculture, especially roses. Regarding water use, the calculated dry season water use of the total sector has increased from 357 l/s to 663 l/s. Although water use has in-creased, reliance on river water has decreased. In 2003, 41%-62% of the total irrigation water necessary in the commercial horticulture sector came from rivers; in 2013, river water ac-counted for just 10-31% of the sector’s total dry season water requirements. Storage water and groundwater grew increasingly important to the horticulture sector during this time, with the usage share of each rising by approximately 15%. In order to assess the impact of the commercial horticulture sector on river water, the depletion of four rivers – Naro Moru, Burguret, Teleswani, Timau – was analyzed during a ten-year period before commercial horticulture started in the study area (1981-1990), compared to a recent ten-year period when commercial horticulture was well-established (2003-2012). The impact that commercial horticulture has had on local river water abstraction varies widely, influenced by the availability (or absence) of water storage facilities and groundwater availability. Currently, alternative water sources are the most important factor in the continuity of commercial horticulture production in the study area, and thus, in the reliable supply of customer demand in Europe.