A STRESSED STREAM ANALYSIS OF STORMWATER IMPACT IN TWO MIXED LAND-USE WATERSHEDS OF THE ROCHESTER EMBAYMENT, LAKE ONTARIO

The ecological and financial impacts of phosphorus on streams, rivers and the coastal zone of Lake Ontario has become a significant issue in the past decade. It is generally assumed that most of this phosphorus load is the result of land-use alterations, particularly those associated with agriculture or development activities. Unfortunately, although often highly successful, attempts to quantify the impacts of land-use practices and alterations on the export of P from small watersheds are few. Compounding this problem is the contribution of municipal storm sewers to streams, creating sub-watersheds. This investigation uses a stressed stream segment analysis approach to determine relationships between land-use and phosphorus export for two small watersheds of the Lake Ontario lake plain region near Rochester, NY that have been identified as 303(d0 impacted water bodies by the NYSDEC. A survey of the watershed has identified three segments for continued long-term monitoring. Total phosphorus (TP), soluble reactive phosphorus (SRP) and turbidity are the key parameters indicating impact. TP concentrations, representative of other monitored parameters, are found to range from a low of 8.1 ug/L during base flow to as much as 1144.5 ug/L during a storm flow event. Evaluating TP concentration data spatially identifies stream segments where TP loading is increased. The three segments identified are mixed land-use, but varyingly dominated by agricultural or suburban residential use. Ongoing monitoring is focusing on specific contributing areas with the identified stream segments.