Univrsity of Tehran Press Geopersia 2228-7817 13 2 2023 11 27 Estimating recharge into the Semnan alluvial aquifer using saturated zone studies _ 415 425 93280 10.22059/geope.2023.358106.648711 EN Bahareh Ekramipour Faculty of Earth Sciences, Shahrood University of Technology, Shahrood, Iran Hadi Jafari Faculty of Earth Sciences, Shahrood University of Technology, Shahrood, Iran Sajjad Moradi Nazarpoor Faculty of Earth Sciences, Shahrood University of Technology, Shahrood, Iran Rahim Bagheri Faculty of Earth Sciences, Shahrood University of Technology, Shahrood, Iran Somayeh Zarei Doudaji Faculty of Earth Sciences, Shahrood University of Technology, Shahrood, Iran 0009-0003-5223-3930 Reza Jahanshahi Department of Geology, Faculty of sciences , University of Sistan and Baluchestan , Zahedan ,Iran. 0000-0003-2931-2377 Journal Article 2023 04 21 The assessment of recharge is one of the most important issues in management and planning of the groundwater resources. In this study, the amount of recharge to the Semnan alluvial aquifer was investigated using methods of water table fluctuations (WTF), chloride mass balance (CMB), water budget and stable isotopes. The parameter is highly important for managing this vital aquifer as over- exploitations for drinking, agricultural and industrial uses occurred, resulting in water table decline with an average rate of about 80 cm annually. Based on the results, the values of recharge into the Semnan alluvial aquifer are estimated about 4.4, 2.5 and 2.1 MCM/year by WTF, CMB and water budget<br />methods, respectively. The isotopic data ( 18 O and 2 H) do not show any significant effects of evaporation on recharge process, confirming the main role of highland recharge in this arid-land aquifer. Combining results of the recharge studies in saturated zone of Semnan aquifer, yields annual rainfall recharge of about 3 MCM, which is about 5% of the annual precipitations. https://geopersia.ut.ac.ir/article_93280_5bfdb4615c7b1e263f6db2f66c1740a5.pdf