The paper analyzes the maximum costs river Podkumok (gauging station in Kislovodsk) and on the small mountain river Eshkakon for the period 1936 - 1941 and 1944 - 2019 taking into account the data of the operation service of the Eshkakonskoye hydroelectric complex, commissioned in December 1989. In the rain flood on June 22, 2002 at the spillway structure of the Eshkakon hydroelectric complex, the operating service recorded a flow rate of about 200 m3/s, and at the gauging station in Kislovodsk on the river Podkumok water flow was equal to 328 m3/s. The authors of the work specified the expenses of rare security for the Eshkakon hydroelectric complex taking into account the consumption of rare security of the rain flood on June 22, 2002.