Data Quality Deterioration in the Lake Tana Sub-basin, Ethiopia: Scoping Study to Provide Streamflow and Water Withdrawal Data

Abstract

Effective water resources management is dependent on having information about the status and distribution of water resources. Having more accurate and comprehensive information on components of the water cycle enables the sustainable development of water resources at basin/ regional levels. In Ethiopia, hydrological data monitoring dates back more than half a century at different locations throughout the country. However, in recent years, there has been a decline in the quality and density of measurements, because some gauging stations are not working properly, rating curves are not updated, or stations are abandoned. More importantly, streamflow data for recent years are not available to users due to the problem of converting water level data to discharge. As a result, proper hydrological assessment is lacking for most basins and made it difficult to understand recent variations in river flow caused by climatic and human factors. Lack of recent knowledge on water availability and use will have increasing implications for the country’s goals of poverty alleviation, increasing agricultural productivity, flood and drought forecasting, and increasing energy production. The Lake Tana sub-basin, source of the Blue Nile River, is one of the locations selected by the Ethiopian government as a growth corridor for development activities, due to its water and land resources. However, this sub-basin also experiences a lack of hydrological monitoring of a good quality and quantity, as evidenced by the recent deterioration of river flow data. Despite booming irrigation activities, information on water withdrawals for irrigation is not available. Water use and water demand by other sectors are not explicitly known. The capability to collect and manage data remains inadequate in the sub-basin due to the lack of adequate financial resources and capacity to maintain and strengthen monitoring networks. This scoping study, conducted under the Future Leaders – African Independent Research (FLAIR) program, was initially planned to understand hydrological changes within the Lake Tana sub-basin. However, after experiencing data challenges, the program prioritized generating primary data and demonstrating possible solution pathways to fill data gaps. We follow a co-planning process with staff from the Abbay Basin Development Office (ABDO) and woreda (district) experts on data measurement procedures, priority gauging stations, development of rating curves, and surveying irrigation water withdrawal sites and water demand sectors. With this approach, this study was able to measure streamflow velocity and use the data to develop rating curves for three key flow gauging stations at Gilgel Abay, Gumara and Ribb, which cover more than 80% of the sub-basin. Water withdrawals for small-scale irrigation schemes were estimated through studies conducted in 15 locations covering five woredas that have a total irrigated area of more than 1,000 ha per woreda. Water demand estimates for urban and rural water supply (drinking and domestic use), livestock, agriculture, industry and hydropower were obtained from government databases of each woreda in the sub-basin. Given that data on water withdrawals/demand were not compiled previously and due to the lack of recent river flow data, this study contributed to reducing the data gaps to support planning and development processes. Furthermore, the data compiled can be used to improve water allocation modeling and planning by ABDO. ABDO is currently working on a water allocation model (Water Evaluation and Planning [WEAP]) using old data and incomplete information on water withdrawals. This study also highlighted the need for a data alliance among stakeholders in the sub-basin. It demonstrated the possibility of conducting such activities with limited financial resources at selected highly relevant locations. We have observed that it is more about commitment, partnerships that benefit data providers and users, and a strong conviction on the value of such data by all stakeholders that can drive the improvement of water data collection for decision-making. Through different projects, the International Water Management Institute (IWMI) has shown the gaps in and opportunities for monitoring hydrological data in various basins. This approach can be upscaled to national level.