Abstract

One of the most significant potential concerns of climate change is to understand changes in hydrological components and subsequent change in lakes water balance. In view of this study, the water balance components such as surface water inflow from gauged and ungauged sub-watersheds, precipitation and evaporation pattern of the natural reservoir and their associated impacts vis-à-vis altering the water balance of terminal Lake Chamo has a major concern in the present study. The raw A1B scenario outputs are characterized by significant biases and hence subjected to bias correction before applying in the hydrological modeling. The bias correction for A1B scenario for precipitation, maximum and minimum temperature was done by using linear scaling approach. This analysis is based on projection of two different scenarios of future time horizons: 2030s (2031-2040) and 2090s (2091-2100). A hydrological model, Hydrological Byråns Vattenbalansavdelning (HBV), was used to simulate the current and future inflow to the lake. The performance of the model was assessed through calibration and validation process and resulted in R2 from 0.64 to 0.81 during calibration and from 0.63 to 0.77 during validation and the relative volume error RVE is from -1.77 to 4.42% at the three stations. Mean annual inflow to Lake Chamo from gauged and un-gauged catchment is 257 mmyr-1. The estimated runoff for the period 2030s and 2090s is 215 and 147mmyr-1 respectively. The result shows that the mean annual inflow is decreased by 16.3 and 42.8% in 2030s and 2090s, respectively from the base time period. The result revealed the maximum and minimum temperatures increase for the two scenarios in future time horizons. However, precipitation decreased in all future time horizons. The A1B scenario reveals the decreasing pattern of lake water storage due to decrease of inflows components such over lake precipitation and surface water inflow in all the future time horizons. In this scenario, the over-lake evaporation is increased by 0.73 and 2.6% at 2030s and 2090s.

Key words: Water balance, Lake Chamo, RCM, A1B, climate variability, HBV model.