The Impact of Irrigation Water Governance and Performance on Environmental Flow in Ketar Subbasin, Central Rift Valley, Ethiopia
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Date
2023-06
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Addis Ababa University
Abstract
Failure to maintain adequate environmental flow in quantity, timing, and quality leads to failure to support ecosystems and human livelihoods and well-being. Irrigation is the main contributor to the reduction of water flows in rivers both in quantity and timing. However, it was not thoroughly investigated especially in subbasins and their constitute catchments where smallscale irrigations are dominating. This study was conducted in the Ketar subbasin of Ethiopia to examine the impact of irrigation water governance and performance on environmental flow. The study considered the irrigation season of 2020/21 and 2021/22 taking Ketar Fowafowate, Ketar Genet, Ketar Torben Unshoo, and Arata irrigation schemes as samples. The study looked in depth at the irrigation water governance status, irrigation performance, and water values as determinates of the environmental flow. Data such as the river flow, irrigation, irrigation water user associations (IWUA), and NDVI were collected from different relevant sources using direct observation, MODIS satellite images, surveys from irrigation farmers of the four schemes, and the central rift valley subbasin. The data were analyzed using various tools FAO cropwat 8.0, Arc GIS, Water Evaluation and Planning System (WEAP) tools and Tennant, Flow duration curve, and local thumb rule approach. The result showed that 73% & 21% of the modern and traditional IWUAs in the subbasin were legally registered and collects an average ETB 1200/year/ha which is insignificant for O&M and proper water management. The water distribution disparity among the four schemes from 3.5 – 8.4 li/sec at farmers' plots. 47% of the respondents depicted their dissatisfaction with the water allocation while 62% are satisfied with IWUAs' decision-making transparency. The study also revealed that the IWUAs are compounded with weak infrastructure management that resulted in substantial water loss ranging from 12 to 49%. Regarding irrigation performance as a determinant of environmental flow, the result showed that schemes and irrigation plots near the water resource performed better than the downstream schemes and tail irrigation plots. The average NDVI values of the four irrigation schemes ranged between 0.32 and 0.54 with the highest and lowest at 0.79 and 0.1 respectively. The distribution efficiency of the four schemes was found 49%, 48%, 57%, and 59% for K. Fowafowate, K. Genet, K.T. Unshoo, and Arata Chufa respectively. The result of the multiple values illustrated diverse but also interconnected 24 community-perceived and articulated water values in CRV. In terms of priority water values, the overall result reflects the basic needs of water for food security. The result further illustrates the pluralistic nature of water value and the dichotomy of preference by people of different backgrounds. This shows that irrigation remains to be the dominant water consumer in the subbasin. In general, the total water demand of the subbasin was 27.7 million m3 per year, which is 7% of the mean annual water resource. There was no unmet demand for the water supply and the livestock in the subbasin. Having these in mind, the environmental flow Ketar at Abura was expected to be as 1.4, 1.5, and 0.27 m3/sec according to Tennant, FDC-Q95, and local thumb rule, respectively. Similarly, Ketar at Fite was estimated to be 0.8, 0.9, and 0.28 m3/sec, in the same order as the methods. The overall result of this study showed that up to zero environmental flow in the small catchments of the Ketar subbasin while the main river course, Ketar, is currently safe. In general, there is a deficit for environmental flow in most of the irrigation schemes downstream in December, January, and February. Hence, expanding irrigation without giving xvii due attention to an environmental flow could lead to more environmental flow risk. To ensure sustainable irrigation development with high water reliability and sound environmental flow, a participatory and implementable water governance policy with tailored technical solutions should come into place. Methodologically, environmental flow estimation and decision support tools must be customized to local ecological requirements by engaging stakeholders (e.g., the local community). Policy-wise, overlapping governance structures are putting multiple water values that are based on environmental flow in CRV under threat. Technically, Ethiopia should standardize irrigation performance measurement by complementing the conventional method with recent remote sensing approaches to alleviate the pressure on environmental flow. Policy directions and decision-making that involve environmental flow and acknowledge its competing uses and aim at reconciling trade-offs are critical for sustainable irrigation development and beyond.
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environmental flow, irrigation water governance, irrigation performance, water values, ecosystem service