The environmental significance of the Tahoe Basin is clearly demonstrated by historic efforts to protect lake and tributary quality through management of naturally diverse watershed ecosystems. The balance between runoff, infiltration, recharge and nutrient transport can be easily shifted through human activities such as forestry, grazing, resource management and watershed development. Subsequent impacts of each activity on source and amount of water and nutrient discharge must be clearly understood if we are to truly reduce nutrient loading, rather than simply re-route the nutrients to an alternate discharge pathway. Our studies have clearly shown infiltration, runoff, erosion, groundwater recharge, and nutrient transport to be heterogeneous and difficult to predict due to such factors as soil water repellency, preferential flow, soil type, plot condition and vegetative cover. We have most recently examined colloid nutrient transport as a mechanism for the cycling of particle- reactive chemicals that may influence lake and tributary ecology in the Sierra Nevada. Such forms may well represent a previously unrecognized significant source of mobile nutrients in the Sierra Nevada.