Streamflow sensitivity to climate and land cover changes: Meki River, Ethiopia

Abstract

Abstract. Impacts of climate and land cover changes on streamflow were assessed using a hydrological modeling. The precipitation runoff modeling system of the US Geological Survey was modified in order to consider wetlands as a separate hydrological response unit. Initial model parameters were obtained from a previously modeled adjacent catchment and subsequent calibration and validation were carried out. The model calibration and validation periods were divided into three. The calibration period was a five years period (1981)(1982)(1983)(1984)(1985)(1986)). The validation period was divided into two: validation 1 (1986-1991) and validation 2 (1996-2002). Model performance was evaluated by using joint plots of daily and monthly observed and simulated runoff hydrographs and different coefficients of efficiency. The model coefficients of efficiency were 0.71 for the calibration period and 0.69 and 0.66 for validation periods 1 and 2, respectively. A "delta-change" method was used to formulate climatic scenarios. One land cover change scenario was also used to assess the likely impacts of these changes on the runoff. The results of the scenario analysis showed that the basin is more sensitive to increase in rainfall (+80% for +20%) than to a decrease (−62% for −20%). The rainfall elasticity is 4:1 for a 20% increase in rainfall while it is 3:1 for a 20% reduction. A 1.5 • c increase in temperature resulted in a 6% increase in potential evapotranspiration and 13% decrease in streamflow. This indicates that the watershed is more elastic to rainfall increase than temperature. The proposed land cover scenario of converting areas between 2000 to 3000 m a.s.l. to woodland also resulted in a significant decrease in streamflow (11.8%). The study showed that properly calibrated and validated models could help understand likely impacts of climate and land cover changes on catchment water balance.

Assessing Impacts of Land Use Changes on the Hydrology of a Lowland Rainforest Catchment in Ghana, West Africa

“…Several studies [9,21,48,49] have applied distributed models to study impacts of land use changes on hydrology as the models are intended to simulate the physical reality of the hydrological cycle, spatially and temporally, which is vital for effective land use planning and water management. The use of physically based semi-distributed model such as ACRU reduces the data requirements that would have been necessary for a fully distributed model, and justifies its application in a data-scarce region such as the Bonsa catchment in Ghana, West Africa.…”

Study on Variations in Climatic Variables and Their Influence on Runoff in the Manas River Basin, China

“…The results showed that a change of precipitation and potential evapotranspiration by 1% would cause a change of runoff by 2.1%-2.5% and 0.5%-1.0%, respectively. Legesse, et al [9] analyzed, quantitatively, the sensitivity of runoff to temperature and precipitation with a modified rainfall runoff modeling system of the US Geological Survey in the Meki River in Ethiopia. It was revealed in the result that the runoff would increase by 80% or decrease by 60%, respectively, if the precipitation increased or decreased by 20%, and the increase in temperature would cause the increase of evapotranspiration by 6% and the decrease of runoff by 13%.…”

Sensitivity of hydrological variables to climate change in the Haihe River basin, China

“…Under this framework, the sensitivity of hydrological variables to climate change was studied all over the world (e.g. Chiew et al, 1995;Fontaine et al, 2001;Jones et al, 2006;Legesse et al, 2010;Ryu et al, 2011). However, because of the uncertainty of structure construction and parameters estimation of hydrological models, some different results would be concluded in the same basin with different models (Sankarasubramanian et al, 2001).…”