Hydrological Alteration Assessment by Histogram Comparison Approach: A Case Study of Erdu River Basin, China

The Erdu River is a small river in Hunan Province. This paper studies the quantitative assessment of the hydrological alterations in the hydrological regimes of the Erdu River caused by the Liujiaping hydropower station. Diurnal streamflow data between the time intervals from 1967-2013 were obtained from the Hengbanqiao station. The histogram comparison approach (HCA) and improved overall degree of hydrological alteration with new classification were used for the assessment. The hydrologic regime alteration was computed by the IHA (indicator of hydrological alteration) indices. As per the improved classification, three indices were altered at low degrees, seven -indices were altered at moderate degrees, eleven indices were altered at high degree and ten indices were altered at severe degree. The overall and improved overall degree of hydrological alteration for the Hengbanqiao station is 72% and 80.49% respectively, suggesting a high and severe degree of alteration respectively. The alteration degree of every IHA indices ranged from 32.29% to 100%. This shows that the current operation mode of Liujiaping hydropower station has severely deteriorated eco-hydrological regimes of the downstream area. Hence, there is an immediate need to operate the reservoir taking into consideration the ecological needs of the downstream areas, in order to preserve the river-ecology of the Erdu River.