The Effects of Constructing and Exploiting Karkheh Storage Dam on the Land Uses and Quality of Regional Water

One of the most important outcomes of dam construction is changing land use and investigating its effect on changing water quality and disturbing ecosystem balance of rivers in dam`s downstream.this study was conducted in the downstream watershed of the Karkheh dam locating in the south-west of Iran to analyze influences of land use change resulting of construction of Karkheh dam on water quality of Karkheh river as one of the indicators for destruction of ecosystem balance of the study river.

In order to conduct the study periodical Land Sat TM and ETM+ images were used to assess land use change before and after construction of the dam. Comparative water quality data collected. Hydrometric station was also used to analyze possible existence of correlation and relationship between land use and water quality changes.

Results of the study indicated that there is a significant correlation between land use change and water quality of the river in the low land of the Karkheh dam at confidence level of 95 and 99 per cent(p-value=0.05 and 0.01) Application of regression models to formulate relationships between area of different types of land use and amount of each one of the observed parameters of water quality indicated that increase in area of irrigated land  due to the providing water is the main factor that tended to deterioration of water quality of rive trench in downstream of the Kharkheh Dam. While allowcated land for irrigated land in the study area is about 76%.

This study indicated that the allowed area allocated to irrigated agriculture was 46% of total basin of Karkheh dam`s downstream. Therefore, increasing irrigated agriculture use was the main reason for reducing the quality of river`s water.