Watershed Resiliency

The New York State Water Resources Institute supports research and outreach collaboration across varied watershed management objectives. A unifying theme of WRI’s collaboration is to increase watershed resiliency. Ecosystems are dynamic systems and the water cycle is a main driver of change in ecosystem state. The water cycle controls seasonal dynamics such as the rate of vegetation growth, as well as extreme events such as flooding or landslides. Perturbation or disturbance events are normal occurrences in all ecosystems. Managing watersheds to increase system resiliency requires implementing techniques that make a watershed less susceptible to disturbance events or that promotes quick system recovery following a disturbance. Toward this goal, WRI collaborates in three broad areas of watershed resiliency: 1) climate change science and communication, 2) stormwater and flooding, and 3) water quality protection (watershed protection and land use).

Hurricane Sandy
NASA image of Hurricane Sandy approaching NY on October 29, 2012.

Historic records provide an indication of the normal range of water cycle dynamics and modeling studies provide insight regarding how these dynamics may change in the coming decades. However, both of these techniques for understanding future watershed dynamics are uncertain. In the northeastern U.S. climatic records for the past decades, including the 1960s drought and subsequent decades of historically high precipitation, are not accurately predicted by General Circulation Models (GCMs) (Seager et al. 2012). The apparent dependence of regional weather on unpredictable atmospheric variability means urban areas need to prepare for water stress from both flooding and drought. In addition to the unpredictability of long-term weather patterns, watershed response to weather events can vary over relatively short distances. High spatial variability in watershed response to the increase in peak precipitation events since 1970 has been demonstrated across subbasins of the Mohawk Watershed. An analysis of stream discharge at Cohoes, NY showed only 9 of 25 peak rainfall events lead to discharge exceeding the historic 99.5th percentile value, indicating that high discharge is not purely controlled by peak precipitation (Shaw et al., in preparation). In contrast, an analysis of the top 65 large flow events since 1965 for the Schoharie Creek (which drains from the Catskills) showed that 47 of 65 events occurred since 1970 (Shaw et al., in preparation). The soil moisture state prior to precipitation is an important factor in determining peak flow events, as well as whether a watershed is affected by tropical storms. Given inherent uncertainty in determining peak water cycle events, such as flooding, increasing watershed resilience can buffer communities from extreme events.

Greenhouse
Green infrastructure helps process stormwater on the landscape. Above is the design criteria for constructing a bioswale from grownyc.org.

Management to improve watershed resiliency includes the built environment, water infrastructure, and land use planning, and WRI supports collaboration in all of these areas. Management to increase the retention time of water within the watershed can increase water storage capacity in times of drought and delay water movement during flooding events. Thoughtful management of natural vegetation (for instance floodplains) and incorporating green infrastructure into road design and drainage in the landscape that supports a watershed can promote the preservation of groundwater recharge and can slow the flow of water from headwaters to estuaries. WRI supported work has identified drainage ditch design as an important tool to reduce the speed of water flow, as current drainage practices increase loss of water from a basin by 20-30% (Buchanan et al. 2013). Preventing building in floodplain is another important strategy for watershed resilience to flooding. Vegetated floodplains can trap sediment and reduce water quality impairment resulting from peak flow events (Aust et al. 2012). WRI looks forward to supporting innovative partnerships that prepare communities to plan for and adapt to watershed dynamics.

References:

Aust, WM, McKee SE, Seiler JR, Strahm BD, Schilling EB. 2012. Long-term sediment accretion in bottomland hardwoods following timber harvest disturbances in the Mobile-Tensaw River Delta, Alabama, USA. Wetlands 32:871-884.

Buchanan, B., Easton, Z. M., Schneider, R. L., & Walter, M. T. (2013). Modeling the hydrologic effects of roadside ditch networks on receiving waters. Journal of Hydrology. 486:298-305.

Seager R, Pederson N, Kushnir Y, Nakamura J. 2012. The 1960s drought and the subsequent shift to a wetter climate in the Catskill Mountains Region of New York City Watershed. American Meteorological Society 25:6722-6742

Shaw S. 2013. Assessing Flood Risk in a Changing Climate in the Mohawk and Hudson River Basins. WRI Annual report