The Impact of Land Use on the Murderkill
River Watershed

This June marks the two year anniversary of the Murderkill River Watershed Tributary Action Team, which was formed to recommend strategies to reduce the river's nutrient loading.  Our January/February issue included an article that discussed some of the successful actions that have been implemented since the team started.  This time we'll discuss land use and its impact on water quality in the watershed.

Land Use

We track land use in the watershed for several reasons.  Different land uses have different water quality impacts.  Land in agricultural and residential uses may impact water quality when excess fertilizer gets into runoff, or  when on-site wastewater treatment and disposal systems are not functioning properly  Industrial and commercial facilities may contribute other types of pollution.   Changes in the amount of land in each use can have major impacts on the amount of impairment to the Murderkill River.  The most recent land use data available is from 2002, which we've compared to 1997 data in Table 1.  (Some of the changes may be attributed to calculation or categorization differences when the data was collected.)

*The Urban category includes residential, recreational, commercial, industrial, transportation, and utilities.

Some uses are beneficial or may have limited or no impact on water quality.  For instance, wetlands provide many benefits to a watershed:

• Acting as a “sink” to filter and clean pollutants and nutrients from runoff, and then assimilate them back into the ecosystem
• Serving as flood protection areas, allowing floodwaters to ebb and flow without human interaction
• Providing groundwater recharge areas, allowing precipitation to reenter the ground rather than flowing over land to the river or bay
• Providing habitat for a plethora of fish, mammals, birds, amphibians and reptiles which rely on the variety of plants and invertebrates found in their local ecosystems.

For years wetlands were considered wastelands that had little value until they could be drained and "reclaimed".  Today, wetlands are protected and are restored in many areas because of their economic value as measured by flood damage prevention, water supply supplementation, and recreational area creation.  Wetlands and water take up about 18.5% of the land area in the Murderkill River Watershed.

Forested and barren lands also provide benefits for watersheds.  Trees and vegetation help to reduce the velocity of flow over land, helping reduce erosion and sediment loading in our waterways. Generally these areas do not contribute excess nutrients or other pollution to waterways.  In 2002, forested and barren lands made up about 12% of the land area in the watershed.

Agriculture and rangeland are broadly defined as those areas which produce and/or support livestock and/or crops.  Agriculture is the most common land use in the Murderkill River Watershed.  Areas with high densities of agriculture are prone to excess nutrient accumulation in ground and surface waters from past fertilizer use practices.  In 2002, agriculture and rangeland used about 55% of the watershed's acreage.  As a result of past practices, the agriculture sector is one of the main contributors to the Murderkill's nonpoint source pollution.  The Murderkill Tributary Action Team is working on recommendations to help farmers identify ways to further reduce the amount of nutrients that end up in the river through the adoption of ever-improving agricultural best management practices (BMPs).  There are several fact sheets for the watershed, discussing ways that farmers can reduce nutrients and protect their farmland, including:

• Agricultural Best Practices (237 kb)
• Transferable Development Rights (182 kb)
• Riparian Buffers in the Murderkill Watershed (50 kb)

These fact sheets were developed and made available at the request of the Murderkill Tributary Action Team.

Urban areas also have a major impact on water quality.  In the Murderkill Watershed, 14% of the land is classified as urban, which includes residential, recreational, industrial, and commercial areas, plus transportation and utility facilities.  As more areas are developed in the watershed, water quality concerns from urban stormwater runoff ( 56 kb) and impervious cover will become an even greater issue.  Residential septic systems ( 217 kb ) may also be a significant contributor to nutrients in the Murderkill River.  Kent County has identified its growth strategy, in cooperation with the State’s strategies and the Livable Delaware program.  The county has a map overlay of the area where the county would like to concentrate development and infrastructure, and you can click here to open the map ( 2.74 MB).

According to the map, significant growth can be expected in the watershed in the future. We are also making recommendations for development practices and residential actions to reduce the amount of nutrients and other pollutants reaching the Murderkill River and its tributaries.  As land use changes, impacts on water quality will also change.  The responsibility to monitor water quality and availability won't change, though...it's everyone’s responsibility to ensure we have a safe and suitable supply of water for our future.