report noted that it often takes many years—often at least ten years—to realize statistically significant water quality results from a given land or nutrient management project or action (NRC, 2009). Identifying nutrient and land management practices that support improvements in water quality is a long-term endeavor that will entail sustained monitoring initiatives in tandem with nutrient management actions. This dual “action-learning” strategy was recommended in the 2009 NRC report and via its recommendation for the Nutrient Control Implementation Initiative (NCII). This spirit of action-oriented learning also is reflected in the USDA NRCS Mississippi River Basin Healthy Watersheds Initiative. The MRBI is a prominent example of pairing nutrient management actions with monitoring activities to improve understanding of system responses.
Much has been learned from long-term monitoring in the Mississippi River basin, primarily at U.S. Geological Survey monitoring sites. The USGS has partnered effectively with states for operation and maintenance of many water quality monitoring stations. As the number of USGS monitoring sites has declined due to budget reductions, in some instances states have been able to step in to keep some sites operating. More long-term monitoring sites will help improve understanding of nutrient sources and nutrient fate and transport across the basin.
Long-term monitoring also is important for field evaluation of conservation practices. Plans for edge-of-field or watershed-scale monitoring will be more effective to the extent they can be conducted for several years in order to evaluate performance of conservation practices under a sufficiently broad range of inter-annual variability.
Interpretation and modeling of water quality data are greatly aided by complementary data on environmental conditions at the time of sampling (e.g., temperature, flow, and precipitation). As was pointed out by many workshop participants, more routine collection of such data in water quality monitoring plans would strengthen the overall water quality database for the basin.
Development and implementation of consistent methods and protocols for evaluation of water quality and conservation practices has enabled significant advances in basin-level analysis and modeling. Continued effort for standardization of methods is challenging but will be critical to the value of these studies.
Several workshop participants noted the value of “paired watershed” studies, which have documented benefits of improved nitrogen fertilizer