Understanding the conditions that enable or constrain success in environmental governance is crucial for developing effective interventions and adapting approaches. Efforts to achieve and assess success in environmental quality improvement are often impeded by changes in conditions that drive outcomes but lie outside the scope of intervention and monitoring. Through historical trend analysis, GIS mapping, and policy analyses of the Yahara River watershed (YRW; the watershed for NTL study lakes Mendota, Monona, and Wingra), we documented how long-term changes in land use, agriculture, and climate act as non-stationary drivers of change that combine to render water quality management interventions less effective and increasingly difficult to assess. These shifting drivers exert tremendous pressure on water quality outcomes but are not captured in snapshot baseline assessments used for intervention planning and evaluation (Fig). This research focuses analysis on the following drivers of water quality outcomes in the Yahara River watershed:
1) Land use change: Key changes include 1) increasing urbanization shrinking the agricultural land base available for manure spreading, resulting in larger risk of high phosphorus loads to downstream water bodies; 2) urbanization increasing watershed impervious surface and construction-site and streambank erosion; 3) decreasing pasture area and increasing row crop area that exposes more nutrient-laden soil; and 4) reductions in nutrient-removing wetland acreage.
2) Agricultural intensification: Agricultural sector change related to the intensification of milk and manure production drives YRW water quality outcomes and is increasingly challenging to address through best management practices. Area dairies produced over 1billion lbs. of milk in 2006. Per cow milk production has increased and the average watershed dairy cow now produces twice the manure it did 40 years ago. More cows and more nutrients have been pushed onto a smaller land base, concentrating manure spreading and increasing soil phosphorus levels on remaining agricultural land.
3) Climate change: Increasing annual precipitation and frequency of heavy rainfall in the YRW result in more surface runoff and erosion of phosphorus-laden soil. As streamflow increases with heavy precipitation events, phosphorus loading increases exponentially. Observations from two major sub-basins draining to Lake Mendota – Yahara River and Pheasant Branch Creek – indicate that 70-80% of the phosphorus load occurs on only 5% of days, making increased frequency of heavy rain events a potentially serious problem for water quality management efforts.
Analysis of these shifting drivers demonstrates challenges facing environmental governance in the context of climatic and socioeconomic change. Lessons about policy interventions and assessment from the YRW suggest how future environmental governance might confront shifting drivers that challenge baseline definition, monitoring and modeling. To enable learning and adaptive governance, scenario planning and transdisciplinary analyses of driving factors of change can complement models and monitoring to better inform environmental intervention design and assessment. Future efforts may also need to engage with the challenging task of confronting drivers of persistent problems through innovative, adaptive and transformative intervention. When shifting drivers remain beyond the scope of management intervention, goals and measures of success may need to be renegotiated.