Hydrogeological Conditions and Discharge Regime of the Verkhne Paratunsky Thermal Springs

The Verkhne Paratunsky thermal springs are the large natural discharge zone of the Verkhne Paratunsky low-temperature nitrogen geothermal field (Kamchatka, Russia). Their hydrothermal and hydrogeochemical history, as well as their discharge conditions, were analyzed based on previous (1966–1996) and renewed (2024–2025) monitoring of the spring regime. The experimental and operational releases at the Verkhne Paratunsky geothermal field in 1975–1984 led to a significant change in the discharge parameters: a decrease in the maximum temperature of the springs from 67 to 46°C and a decrease in the total mineralization (a 2‒2.5-fold decrease in Cl and SO₄), while the flow rates of the entrained springs (3.5‒8.2 L/s) are close to the initial values before the start of tests. The flow tests carried out at the Verkhne Paratunsky geothermal field in 1975‒1984 led to a significant change in the discharge parameters: a decrease in the maximum temperature of the main springs from 70 to 30–35°C, a decrease in the flow rate from 7.7 to 2.9 kg/s, and a decrease in the mineralization by two times or more (all in average annual terms). By 2025, the flow rates of the main captured springs had recovered to 5 kg/s, the temperature to 49°C, and the mineralization to 50–65% of the initial value. Using the chloride tracer method, an updated assessment of the deep component of the total discharge of the Verkhne Paratunsky springs was estimated varying from 6.3 kg/s (March) to 21.9 kg/s (May) in the annual cycle.