Point sources correspond to inflows to and outflows from river nodes, including inflows from demand sites, wastewater treatment plants, tributaries (only if that tributary is not also modeled in QUAL2K) and net decreases in reservoir storage, and outflows to demand site (withdrawals), diversions, reservoir evaporation, and net increases in reservoir storage. The location of the QUAL2K point source is the distance marker for the WEAP node. For inflows, QUAL2K needs to know the concentration of each constituent in the inflow; for outflows, the concentration is irrelevant. See Reservoirs and QUAL2K for details on how reservoirs are handled.