ИСТИНА

The water discharge dynamics of small, urban rivers can be highly variable and complex. Understanding these dynamics and their underlying causes is highly needed for our awareness of water discharge fluctuations of ungauged basins, especially in the face of climate change and urban sprawl. Our work is focused on a small ungauged river Lipovka (Lipetsk, Russia). It has a 50.1 km² urbanized watershed with an outlet in the Komsomolsky pond in the city center. To study the water regime of the Lipovka river we used a series of independent methods. Based on in-situ measurements in spring 2022 we estimate the water discharge with a 1% annual exceedance probability according to the regulatory document SP 33-101-2003. Furthermore, we used data from the Lipetsk meteostation to run a Hydrologiska Byråns Vattenbalansavdelning model (HBV) to simulate a daily hydrograph for the 2005-2022 period. A set of calibration parameters provided at http://www.gloh2o.org/hbv/ were used for the initial run. Later, an HBV model was calibrated based on the regional surface/ground runoff relationship and snow water equivalent (NSE = 0.86). Overall, we found that both methods give controversial results. The anticipated freshet discharges with a 1% annual exceedance probability are 0.69 (HBV) and 0.52 (SP) m³/s. While rain flood discharges are 0.45 (HBV) and 0.57 (SP) m³/s. Yet we tend to believe that HBV does a better job of predicting the maximum water discharge. However, more precise modeling is still needed for extreme events forecasting and accurate assessment of their effect on the urban environment.