Small rivers in Latvia are assessed by biological assessment system that is based on examination of macro invertebrates as one of the most stable cenosis of running water ecosystem. Using this system of classification, Latvia's rivers are classified in seven quality classes from oligosaprobity (clean waters) to polisaprobity (heavily polluted). According to mentioned biological evaluation system water quality of small rivers varies from slightly polluted to heavily pollute (e.g. Rivers Gailupite, Marupite).

The situation is the worst in the Hapaka channel, the small rivers Lacupite, Marupite and Smerlupite. The indicators of surface water contamination are the chemical oxygen demand (COD) and the biological oxygen demand (BOD). These indicators stand at critical levels in Lake Velnezers and the city canal, also in the Smerlupite and the Hapaka channel where these concentrations exceed the maximum permissible several times (see Figure 38 ). 

According to the data of municipal monitoring  (see Location of the monitoring sites ) waterquality in those water bodies and waterways that are used as fisheries (the Bullupe, the Daugava, Lake Kisezers,   Lake Jugla, the Vecdaugava) can be considered satisfactory, however, considerable contamination with organic substances and ammonium could pose serious future threat to the oxygen conditions and the nutrition base for the fish.
Two lakes of the City - Kisezers, Juglas Lake are designated as Cyprinid waters. The population of fish stock of theses lakes is assessed as self-sustainable. The data of the period from 1995 to 1999 show thatNH₄/N concentrations in 1998 are higher (0.20 mg/l) as national target values (<0.16 mg/l) for mentioned waters.