Evaluating the influence of drought on water availability in Longoromit dam, Karamoja region.
Ayenya, Pirmer Patricia
Nandigobe, Braveline Wycliff
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Droughts are one of the most prevalent types of weather-related disasters, characterized as extended periods of below-average water availability. The immediate consequences of drought include water-supply shortages especially in valley dams and reservoirs, destruction of ecological resources, forest fires and losses of agricultural production resulting in famine, human suffering, death and abandonment of whole geographic regions. These effects are vastly felt in the Kaabong, Karamoja region, North Eastern Uganda. Valley dams like the Longoromit dam have been constructed in the recent past in the Karamoja region in North Eastern Uganda, to aid the pastoral community reserve some water for their animals, and also cater for irrigation needs. However, due to the high prevalence of droughts, the Longoromit dam, which is the second largest in the Karamojaregion is reportedly drying up. This study therefore sought to evaluate the influence of drought on water availability in Longoromit dam. The specific objectives for this study were: (a) To assess the frequency and intensity of drought in Karamoja over 30 years, (b) To determine the water level fluctuations (storage) in the Longoromit dam, (c) To assess the impact of drought on the dam’s water availability over the 12 years of its existence and (d) To devise remedial measures for the effects of drought on water availability in the dam. The Standardized Precipitation Index (SPI) was used to characterize drought occurrence and frequency over a period of 30 years (1991-2021). A Water Balance Model (WBM) was then used to obtain the water level fluctuations in the dam from 2010 to 2021. Hydrological modeling was carried out using the HEC-HMS Model to generate the inflows into the dam, the results of which were an input into the Water Balance Model. Comparison between the Standardized Anomaly Index (SAI) and the dam water levels was then done. Drought mitigation measures (structural and non-structural) that can be taken up to better manage droughts in the study area were also suggested in this study. The key findings of this study were: (1) Drought greatly affected the water levels in the dam with SPI values dropping to as low as a minimum of -1.3860 (in April 2017), a period when the dam was first reported to dry up. In November and December 2021, the SPI values fell into the negative zone again, an indication of a drought which led to the drying of the dam in early 2022. Longoromit experienced ten (10) drought periods between 1991 and 2021, four (4) of which were experienced after 2010. The area initially had a drought return period of 3 years before 2010 which reduced to 2.75 years after 2010. This implied that droughts became more frequent after 2010. (2) There has been high water stress on the dam not only from Loyoro sub-county, but from the neighboring sub-counties of Sidok and Lodiko as well and this affected the dam water levels too. In 2021, the change in storage of the dam was calculated at -0.686m, an indication of the dam drying up before even accounting for water consumption from the neighboring sub-counties. The dam which was initially designed to cater for 40,000 heads of cattle, was feeding approximately 58,000 heads of cattle by the end of 2021. Since drought was found to significantly affect the water levels, authorities should put emphasis on drought mitigation measures in the area.