Generally, peak phosphorus flows in watershed streams occur in May and June, during peak snowmelt season. But in winter, rain events can produce some of the highest peak phosphorus flows. On the other hand, soil under a snow pack is frozen, so rain and melted snow can t soak into the ground. When rain falls directly on coarse Tahoe Basin soils, it s likely to soak in. That water then flows underground to streams, dissolving phosphorus, carrying it to streams, and producing higher phosphate concentrations.
Similar processes occur during snowmelt periods.
Hatch also correlated stream-phosphorus loads with various watershed characteristics. Some correlations seem obvious. For example, because of the Sierra rain shadow effect, precipitation is higher along the west shore of the Tahoe watershed than it is along the east shore. And watersheds with higher precipitation have higher stream discharges and phosphorus loadings. Similarly, watersheds with larger drainage areas, steeper terrain and long channel lengths have larger phosphorus loads.