Evaluation of available surface water resources in Qarah Tikan border basin using satellite products and GIS

In the present study, the Qarah Tikan river basin in particular the subbasin of Qarah Tikan Village has been studied. This is located in the northeast of Iran in proximity to Turkmenistan and among the basins without ground station data. IMERG-Final satellite precipitation products, ERA5-Land reanalysis temperature and GLEAM evapotranspiration were used to identify and evaluate the basin. The evaluation results showed that the reanalysis temperature product has high accuracy in temperature estimation and the satellite precipitation product has a high correlation with precipitation data. Therefore, the combination of satellite products with ground station data leads to proper runoff estimation in ungauged basins and hydrometric stations. Based on this, estimating the amount of water available in the basin in different months indicates the possibility of storing about 11.8 million cubic meters per year to meet the needs and agricultural development of the region. 

In this study, in the Qarah Tikan basin, as ungauged basin in the general water balance equation was used to calculate the available water. In this equation, GLEAM global data (Shiklomanov, 2000) used for actual evapotranspiration and environmental needs obtained by the Lyon method were considered as output components of basin. In addition, the inflow to the basin, which was obtained from the hydrometric station of the upstream basin, and the precipitation, which was obtained from IMERG-Final-V06 (Huffman et al., 2019) satellite data were considered as the incoming components to the basin. To calculate the environmental needs of the Lyon method, the monthly runoff of the basin is required for which Justin's experimental method was used. As input data for Justin's experimental method, monthly runoff with adjacent basin from the hydrometric station and precipitation of the basin, monthly temperature of IMERG-Final satellite precipitation data and ERA5-Land were used espectively. By using ArcMap and DEM the slop and area of the basin was produced. 

The results of evaluating monthly temperature data showed that these data have a high ability to estimate the temperature and is reliable in remote areas where there is no weather station and ungauged basin. According to the comparison of satellite precipitation data and ground stations, it can be said that although they do not have high accuracy in estimating precipitation, but they have a good correlation and estimate precipitation with appropriate accuracy. Precipitation in 3 stations is underestimated and overestimated in 2 stations. Based on the long-term average, the annual rainfall of the basin is about 225.9 mm. On the other hand, a study of evapotranspiration data from the GLEAM shows that the long-term annual average is about 194.4 mm, which peaks in the spring due to greater access to water and rising temperatures. Thus, about 86% of the basin rainfall in the evaporation process is out of reach. The annual inflow to the basin was about 15.9 million cubic meters and the annual runoff from rainfall in the basin according to the Justin method was about one million cubic meters. Furthermore, with the aim of maximum sustainable use of basin water resources, the outflow runoff of the basin was considered equal to the downstream environmental needs. Thus, based on the Lyon method, the annual environmental need to maintain the stability of the river was determined to be about 7.5 million cubic meters. As a result, in terms of rainfall, runoff, evapotranspiration and environmental needs, the annual amount of water available in the basin for different purposes is about 11.8 million cubic meters. 

In this study, the distribution of these water resources in different months has been determined and the results indicate that to meet the demand of the agricultural sector in summer and also control winter and spring floods, planning for the design and construction of a storage dam should be on the agenda. In this case, the output of the basin will be adjusted. Once again emphasizes the importance and ability of remote sensing and GIS in the study of water resources in ungauged basins without proper ground station statistical data.