Assessing the Land Use/Cover Dynamics and its Impact on the Low Flow of Gumara Watershed, Upper Blue Nile Basin, Ethiopia

Abstract

Land cover and Climate change are very important issues in terms of global context and their responses to environmental and socio-economic drivers. The dynamic of these two factors is currently affecting the environment in unbalanced way including watershed hydrology. In this paper the impact of land use/cover change on stream flow particularly on low flow were evaluated through application of the model Soil and Water Assessment Tool (SWAT) in Gumara watershed, Upper Blue Nile basin Ethiopia. The land use/cover data were obtained from Land Sat image and processed by ERDAS IMAGINE 2010 software. Three land use land cover data; 1973, 1986, and 2013 were prepared and these data were used for base map, model calibration and change study respectively. So, as to evaluate the effect of land use/cover change on low flow of the catchment, the stream flow was simulated by changing 1973 and 2013 LULC but the climate data, which is 1973-1982, was used and it was constant. The low flow of the catchment for these two decades was extracted in simulated flows by Seven Day Sustained (SDS) low flow separation method. The model (SWAT) was calibrated by 1986-1991 climate data and 1986 land use land cover data by using 11 important model parameters selected by sensitivity analysis. The consistency of values of those calibrated parameters was also validated by 1992-1995 climates and with the same land use land cover data. Based on the result, the extreme low flow of Gumara watershed has been decreasing from 0.53 m 3 /s to 0.43 m 3 /s which showed decreasing by 0.1 m 3 /s that is 18.87%. From the overall results of the study, it is possible to conclude that land use land cover change has been influencing the low flow or dry season flow of the catchment. This study has been designed to show how much the land use/cover has been changed and affects the low flow or dry season environmental flow of the catchment. The result has showed some indications that there has to be restoration activities on the land use cover nature of the study area.

Hydrologic Trends in the Upper Nueces River Basin of Texas—Implications for Water Resource Management and Ecological Health

“…As a result, land use changes in the NRB, while minimal, could have still impacted the hydrological dynamics in the region. Furthermore, studies by [68,69] explain that land use changes can lead to declines in stream discharge in areas that are susceptible to low flows. The minimal LULC modifications could therefore signal an increase in human consumption along the course of the different stream segments, potentially leading to decreased streamflows as less water arrives to the HCDN gauges.…”

Review, impact of land use/cover change on soil erosion in the Lake Tana Basin, Upper Blue Nile, Ethiopia

“…So the impact of any disturbance will be minimal when catchments are of regional or larger scale. The dynamic of land use land cover is primary cause to altering the watershed hydrology (Chakilu and Moges 2017).…”

“…Land use land cover of the watershed is interesting character to explain the hydrological process of the watershed. The extent and rate of land use/cover change between 1973 and 2013 were studied by Chakilu and Moges (2017). Chakilu and Moges (2017); (Wubie et al 2016) reported that significant change of other land use (grass, bush and forestland) to cultivated land was observed.…”

“…Only 479.36 km 2 (37.7%) of land was covered by cultivated land in 1973 whereas it was about 961 km 2 (75.6%) in 2013. The annual change of the watershed from other land use to cultivated land was 1204 ha yr −1 (Chakilu and Moges 2017).…”

Change in Stream Flow of Gumara Watershed, Upper Blue Nile Basin, Ethiopia under Representative Concentration Pathway Climate Change Scenario

“…Sensitive parameters which have significant influence on stream flow simulated by SWAT model were selected by sensitivity analysis process. Selected parameters are similar with the previous study done by [14]. The model efficiency was evaluated by using statistical variables determining the fitness of simulated stream flow with observed data.…”