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Research on the sources, fate, and effects
of pollutants in coastal watersheds provides valuable insights to better
manage coastal watersheds. But the real breakthroughs in protecting estuarine
water quality take place outside the field and lab and inside town hall
at the monthly meetings of the local planning and zoning boards. Local
officials are key to managing local water quality by updating comprehensive
plans, approving zoning changes, and reviewing subdivisions. Through these
routine decisions, they can dramatically reduce the risk of pollution
to coastal waters. Town planners, council members, and volunteer board
members have a new resource to help them in their decision making: research
results distilled in a format that they can readily use, and watershed
assessment tools using computer-generated maps to target high-risk locations
for pollutant movement.
Through the Municipal Watershed Training
Program, URI faculty, Cooperative Extension water quality specialists,
and student interns provide scientific expertise to help community leaders
reconcile population growth and development demands with water resource
protection goals (Watershed Assessment at URI). A new tool used in this
work is the Cooperative Extension's model for assessing watersheds, the
Method for Assessment, Nutrient Loading and Geographic Evaluation of watersheds
(MANAGE), which is used by URI staff in conjunction with community leaders.
(See Watershed Assessment at URI)
URI Cooperative Extension staff provide Geographic Information System
(GIS) skills and expertise in watershed management science. In turn, town
representatives and citizens share their knowledge about local land use
to enhance map data, select future land-use scenarios for analysis, and
decide how the results will be used to protect or restore local water
quality. The assessment process takes place in a series of four or five
meetings between a small group of town representatives and Cooperative
Extension staff. This provides an opportunity for local participants to
comment on draft results and guide the assessment. The local group also
decides how the results will be shared with other town officials and the
public. Most importantly, the local committee suggests realistic management
actions the town can take to better protect or restore local resources
based on the assessment findings.
MANAGE is a watershed assessment tool that
uses computer-generated maps to take a first-cut look at pollution risks
posed by land use and landscape features. Designed as a system to support
land-use decision making, MANAGE identifies sources of pollution to watersheds
and groundwater aquifers. By analyzing maps, summarizing watershed characteristics,
and estimating nutrient sources, MANAGE compares the effect of future
land-use patterns on local water resources and evaluates the effectiveness
of stormwater and wastewater management practices in reducing pollution
risk.
The primary source of data used for assessment
is the Rhode Island Geographic Information System (RIGIS), an extensive,
high-resolution database available to Rhode Island communities. MANAGE
accesses the RIGIS database through the URI Environmental Data Center.
To predict how continued development might affect water quality, we must
have data on soil types and land use. We can then map future land use
showing full development based on town zoning or land-use planning. This
allows town officials to envision the effect of future growth and to identify
the type and location of potential pollution threats.
MANAGE generates three types of assessment
results: pollution source hotspot mapping, a rapid screening of potential
high-risk areas; watershed indicators that measure generalized ecosystem
health based on soil and land-use characteristics; and a nutrient loading
component that incorporates the results of research on the sources and
fates of nitrogen. It generates a hydrologic budget with which to compare
alternative development scenarios.
All three types of results give town officials
a way to target limited resources and control the most serious pollution
risks. Hotspot mapping is most effective in allowing decision makers to
visualize problem sites. The initial premise is that high-intensity land
uses are more likely to generate pollutants than less intensive uses.
The probability that pollutants generated will actually reach groundwater
or flow into nearby streams and ponds depends on soils and proximity to
receiving waters.
MANAGE uses soil permeability and water
table depth data to locate areas where rainwater and accompanying pollutants
are likely to either seep into the ground or run off the surface to nearby
wetlands and streams. These hydrologically active soils reveal pathways
of water and pollutant movement via groundwater recharge or by direct
flow through surface drainage networks. Wet soils with high groundwater
are not isolated in the landscape but are connected to small headwater
streams and wetlands in an extended drainage network. Maintaining this
drainage network preserves natural pollutant removal functions, promotes
infiltration, and protects the water quality of downstream waters.
The MANAGE hotspot analysis combines high-intensity
land use and high-risk soil features to screen hotspots where pollutants
are typically generated and where offsite movement is also likely. In
the hotspot mapping example, high density, unsewered residential development,
commercial land use, and active cropland are overlaid with soils having
a shallow water table, revealing potential hotspots for stormwater runoff
and septic system failure. (See map.)
Additional map analysis can highlight risks to groundwater in very sandy
soils where pollutants can move unimpeded into aquifers, in shoreline
areas that have lost protective forest cover, and areas where soils are
easily eroded. Targeting hotspots efficiently narrows potential problem
areas for follow-up field investigation, focused public education, or
pollution remediation.
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