Assessment of hydro-ecological alteration of Halil-Rud Basin and analysis of the role of operating dams in causing it

However the role of water in sustainable development is vital, the launched infrastructure projects of Integrated Water Resources Management Plans in recent years have not been able to completely maintain the balance between human consumption for socio-economic activities and the water needs of natural ecosystems to guarantee the sustainable life for riverine ecosystems. In this regard, this research investigated the hydrological effects and ecological consequences of the construction of dams in the upstream basin of Jiroft Dam as the key water supply zone in the western Jazmurian watershed, which is also known as Halil-Rud River.

In this research, the significance of the long-term changes of the mean annual discharge in the rivers of the study area at the hydrometric stations of Solatni, Baft, Hanjan, Meydan, Qale-Rigi, Konarooiye and Hossein-Abad, as well as the alterations in the mean annual precipitation of rainfall gauges in the period of 38 years (1980-2018) have been analyzed by Mann-Kendall Test and then 33 hydrological parameters (based on the daily discharge of Hossein-Abad hydrometric station in the mentioned period) as indicators of ecological needs (which is affected by the Baft and Jiroft reservoir dams) have been analyzed by using the variability range approach and IHA software in two periods before and after the construction of the dams.

According to the Mann-Kendall test results, although the mean annual discharge in the rivers upstream of Jiroft dam has had a significant drop at the level 95 and 99% of discharge during the past 38 years, the trend of change in the mean annual precipitation in the same period, except one station (Hanjan), was not significant and this difference was due to the negative effects of dams construction and it was also confirmed by the output of the IHA model. It should be noted that based on the output of the mentioned model, 33 hydro-ecological features of Halil-Rud river flow showed fundamental alterations since the operation of Jiroft Dam (1992), but the operation of Baft Dam upstream of Jiroft Dam in 2008 has led to intense negative effects of flow characteristics (outside the acceptable range of ecological variability) in Halil-Rud River.

In order to prevent the magnification of the water crisis, the cumulative effects of the construction of chain dams should be considered using hydro-ecological approaches, as well as the water allocation programs, especially the environmental flows should be revised according to the upstream developments of each dam basin, so that the sustainable socio-economic needs as the goals of integrated water resources management would be provided and also the health and survival of the natural ecosystem would be guaranteed.