The Impact of Karkheh Dam and Meteorological Parameters on the Annual and Peak Regime and Flood Plains of Karkheh River

Karkheh River, as the third largest river in Iran, flows a large volume of water to the Khuzestan plain every year. The construction of the Karkheh Reservoir Dam, along with several advantages, widely affects the river flow in its downstream. Ignoring the effects of these structures on the elimination or reduction of river flows, especially flood capacities, leads to investment in agriculture, industry and urban development along rivers, downstream of dams and in flood high-risk areas.

In the present study, the trend of changes in the annual and flooding regime of Karkheh River over time and in the relationship with the establishment of Karkheh Dam were investigated. For this purpose, four statistical tests (Pettitt, SNHT, Buishand and von Neumann) were used to examine the homogeneity of peak and average annual flow data at the downstream of hydrometric station and to determine the points of change and mutation. In order to determine the role of climatic parameters on river discharge, Pearson correlation test was used.

According to the opening of Karkheh Dam in 2001, the results of the study showed that the flood peak discharges in the hydrometric station downstream of the dam (Pay-e-Pol station) was equal to 1978 cubic meters per second, in the period of 32 years before the Karkheh dam opening, and with a significant reduction of 78%, is equivalent to 417 cubic meters per second in the 16 years period after the dam opening. Therefore, considering the removal of flood peaks immediately after the construction of Karkheh Dam, we can definitely observe the effect of the dam on controlling the flood peaks of Karkheh River. The results showed that the highest peak discharge correlation with SPEI parameter, at 95% significance level. Also, monitoring of satellite images show that before the opening of Karkheh Dam (2001), the floodplains were covered by water in flood conditions and after this year, despite the occurrence of floods and high peak discharge reports in Karkheh River, no water intake from Karkheh River has been observed in the floodplains.

The flood regime of the River downstream of Karkheh Dam has indicated a decreasing trend due to changes in climate drought index since 1997, which has had a steady trend since 2001 due to the opening of Karkheh Dam and shows the control of floods by the dam.