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Hydrometric stations are important in most countries because of the application and importance of the data obtained from these stations. It is necessary to choose the best place for their establishment according to the cost of constructing hydrometric stations. The aim and innovation of this research are to optimize the location of hydrometric stations using Bat's meta-heuristic algorithm and interpolation methods, which information transfer entropy theory and Bat's algorithm were used to maximize the average amount of information transfer entropy. For this purpose, the data of 43 hydrometric stations of Karkheh basin in western Iran in period of 1991–2015 were used. In this research, two scenarios were investigated in order to improve the entropy of information transmission between stations. In the first scenario, using the kriging method to prepare the flow distribution map in the region and choosing normal kriging with spherical variogram as the best model to fit the average annual flow data and using the Bat algorithm to increase the correlation coefficient between the data and assuming no none of the available stations, 43 points were used to redeploy stations with higher average entropy in the region. The results of this scenario showed the concentration of new stations in the central and eastern areas of the basin. In the second scenario, the amount of entropy of information transfer at the regional level was calculated and 18 potential points were recommended for the establishment of new stations. The obtained variogram for the discharge of the basin showed that the range of influence is low and it is necessary to establish the stations at a close distance. [ABSTRACT FROM AUTHOR]

Groundwater assets are the foremost imperative assets of freshwater accessible to people especially in arid and semi-arid regions. For the investigation of temporal changes in groundwater nitrate pollution and the role of agriculture and other sources in the pollution of groundwater, the information on 42 drinking water wells with suitable distribution in the plain in Bouin-Daran Plain in the center of Iran was used. The results showed that the amount of hydraulic conductivity in the plain for different areas after calibration in steady state was calculated between 0.8 and 34 m/day. After calibrating the model in permanent conditions, the model was calibrated in non-permanent conditions for 2 years. The results showed that in a wide area of the region, the nitrate ion concentration has values of more than 25 mg/L. This shows that the average concentration of this ion in the region is generally high. The highest level of pollution in the aquifer of the plain is related to the southern and southeastern parts of the plain. Due to the agricultural activities with the use of large amounts of fertilizers in this plain, there is a potential for pollution in all of the places, and it requires codified and executive planning for agricultural operations as well as the use of groundwater sources. The DRASTIC vulnerability estimation method is only useful for estimating the areas that have a high potential for contamination and according to the validation tests, it has also provided a suitable estimate. [ABSTRACT FROM AUTHOR]