Gediz Basin, located in the western part of Turkey constituting 2% land of the country, has an important groundwater potential in the area. Alasehir sub-basin, located in the southeast of the Gediz Basin and subject to the extensive withdrawal for the irrigation, constitutes the study area. Natural recharge to the sub-basin due to precipitation is numerically investigated in this study. For this purpose, 25 research wells, whose depths range from 20 to 50 m, were drilled to observe the recharge and collect the necessary field data for the numerical model. Meteorological data were collected from 3 weather stations installed in the study area. The numerical model HYDRUS was calibrated using the field water content data. Soil characterization was done on the core samples; the aquifer characterization was performed, and the alluvial aquifer recharge due to precipitation was calculated. As a result, the computed recharge value ranges from 21.78 to 68.52 mm, with an average value of 43.09 mm. According to the numerical model, this amount of recharge corresponds to 10% of the amount of annual rainfall.

Scaling is frequently observed in geothermal fields and reduces the energy harvesting of power plants. Recently, Sb-rich deposits have developed in many fields around the world. Various polymeric macromolecules have been used as antiscalants to mitigate the formation of scale. Testing potential commercial antiscalants in field conditions is a tedious and costly process. The artificial synthesis of geothermal deposits in the lab is a more practical and economical way to test the performance of antiscalants. This study obtained a Sb-rich deposit by refluxing SbCl3 and Na2S·3H2O in 18 h. The product was found to be a mixture of Sb2O3 and Sb2S3. We examined the performance of antiscalants such as poly(ethylene glycol), poly(vinyl pyrrolidone), Gelatin, and poly(vinyl alcohol) of various molecular weights at 5 to 100 ppm. The formation of Sb2S3 is suppressed in the presence of the polymeric antiscalants. The dosage was found to be critical for the solubilization of Sb-rich deposits. Gelatin of 5 ppm showed the highest performance under the conditions employed in this study. While low dosages improve the concentration of [Sb3+], high dosages are required to increase the solubility of [S2-]. Moreover, the amount of deposit is reduced by 12.4% compared to the reference (in the absence of any polymeric molecules). Thus, comparatively, Gelatin shows the most promising performance among the molecules employed.

The issue of groundwater recharge has gained importance in countries where there is not enough water supply to the aquifer. However, groundwater recharge is a difficult parameter to determine. This difficulty stems from factors such as the location of the area to be studied, time, cost, and hydrological data. Numerical, isotope, and chemical approaches are used in groundwater recharge investigations. Numerical and chemical approaches are more costly and time-consuming than chemical approaches. This study aims to ascertain alluvial aquifer recharge in Alaşehir (Manisa) sub-basin using chemical approaches (Chloride Mass Balance Method) and its applicability. For this purpose, research wells were drilled at 25 different points in the alluvial aquifer, water sampling was done in wet and dry periods, and rainwater water samples were collected. Groundwater recharge was calculated by using chemical approaches from the chloride concentrations of the water samples collected. An annual average of 74.84 mm of recharge was found in the Alaşehir sub-basin. This value corresponds to 16.38% of annual rainfall. At the same time, it was examined the groundwater and geothermal mixing mechanism to demonstrate the applicability of the Chloride Mass Balance Method. It was concluded that geothermal fluid in Alaşehir sub-basin mixed with groundwater at a rate of 17%. Keywords Groundwater recharge • Alaşehir sub-basin • Gediz basin • Chloride mass balance method (CMB)This article is a part of the Topical collection in Environmental Earth Sciences on "Water Problems in E. Mediterranean Countries" guest edited by H. Gökçeku, D. Orhon, V. Nourania, and S. Sozen.

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<p>Scale problems in geothermal power plants are one of the reasons that reduce power plant efficiency. Silica scaling, calcite scaling, and sulfide scaling are the most common scale types in geothermal power plants. These scale problems in geothermal power plants can be seen in geothermal wells and surface equipment systems. In this context, various measures should be taken to control the scale problems in geothermal power plants. In this study, the stibnite scaling observed in the preheater system of the Germencik geothermal power plant in the west of Turkey is discussed in full detail. Possible types of scale that may occur in the geothermal wells in the power plant were revealed, and the optimum reinjection temperature was determined for stibnite scaling, which reduces the efficiency of the power plant. Within the 3D modeling of the geothermal power plant and different geochemical models, the precautions to be taken at the power plant are examined in all details.</p><p><strong>Keywords</strong>: Stibnite, Scaling, Binary power plants, Germencik, power plant efficiency</p><p><strong>Acknowledgments: </strong>This study has received funding from the European Union’s Horizon 2020 research and innovation programme under agreement, REFLECT Project,  No: 850626.</p>