Using the GR4J Conceptual Model for Runoff Simulation in the Ussuri River Basin

The open-source low-parametric con cep tual hy dro log i cal model GR4J was used for run off sim u la tions of 17 nested catch ments of the Up per Ussuri River ba sin with ar eas rang ing from 133 to 24400 km2, in clud ing the Kirovskii out let. The data of stan dard hydro meteoro logi cal ob ser va tions of Primorye Administration for Hydrometeorology and Environmental Monitoring were used for the model calibration and verification. Runoff simulations were performed with a daily step. The criteria commonly used in hydrological community, namely, the Nash-Sutcliffe model efficiency coefficient (NSE), coefficient of determination (R2), and bias (BIAS) were used to as sess the mod el ing ef fi ciency. According to the specified criteria, modeling results are mostly in "satisfactory" or better categories. The base of the unit hy dro graph expectedly in creases with the catch ment area, but there were no other relationships found between the values of calibrated model parameters, the annual water content, and the main morphometric pa ram e ters of the catch ments. It was shown for the stud ied catch ments that the sta bi li za tion and the max ima of the mod el ing ef fi ciency scores are reached at the catch ment ar eas of 1200-1700 km2. The in flu ence of rep re sen ta tive ness of the weather sta tion net work on the mod el ing efficiency was demonstrated using complementary meteorological observations from experimental catchments in the Up per Ussuri ba sin for the sim u la tion of the cat a strophic flood in 2016 that was caused by typhoon Lionrock.