1.	Monitoring Water Withdrawal and Streamflow Data for Effective Water Resources Management in Lake Tana Sub-Basin

Addisalem Genet Fekadu; Meron Teferi Taye; Alemseged Tamiru Haile

doi:10.20372/ajwes.v1i1.1700

Addisalem Genet Fekadu Abbay Basin Development Office, Bahir Dar, Ethiopia
Meron Teferi Taye International Water Management Institute, Addis Ababa, Ethiopia
Alemseged Tamiru Haile International Water Management Institute, Addis Ababa, Ethiopia

DOI: https://doi.org/10.20372/ajwes.v1i1.1700

Keywords: Irrigation Withdrawal, Streamflow, Monitoring, Spot Measurement, Lake Tana, Gumara

Abstract

The Lake Tana sub-basin is one of Ethiopia's growth corridors with plans that include irrigation expansion. Despite the basin's expanding irrigation activity, there is little information on the rate of irrigation expansion, water withdrawal for irrigation and its impact on the sub-basin's water resources. This study focused on monitoring irrigation water withdrawal from small-scale irrigation schemes and the spatial variation of streamflow in the Gumara River, a major tributary to Lake Tana. For the irrigation water withdrawal monitoring small-scale irrigation schemes from seven districts that use river water diversions were chosen. The command areas of these irrigation schemes range from 20 to 200 ha of land. The monitoring was conducted for two years during the dry season when irrigation activities are dominant. Spot discharge measurements for Gumara River were done at seven locations on the main river at downstream and its tributaries at upstream. The results show that irrigation water withdrawals can range on average from 559 m³ day^-1 to 17824 m³ day^-1 at different schemes. The amount of water diverted mostly correlates with the size of the irrigated area and the size of the rivers. However, at some locations inefficient use of water was observed as the amount of water diverted was large for a relatively smaller irrigated area. The eastern part of the basin experiences lots of irrigation. The Gumara River at different locations showed water scarcity problem. At the downstream within a few kilometres difference between two locations where spot measurements were taken the discharge dropped by 2.8 m³/s during medium flow season. This suggested that there is substantial irrigation practice along the Gumara River, which was also confirmed through irrigation sites survey. Therefore, this study promotes monitoring irrigation water withdrawals and streamflow data at different locations to better manage the sub-basins water resources and avoid localized water scarcity.