CHAPTER 2 – LITERATURE REVIEW
Location in Virginia
The James River Basin contains the Maury River, Rivanna River, Appomattox River, Hampton Roads, Nansemond River and the Elizabeth River sub-basins (Mostaghimi et al., 1995). The James River Basin extends from above the Maury River; between the Rivanna and the Maury Rivers; between the Rivanna River and the Fall Line, the imaginary line extending through the cities of Emporia, Petersburg, Richmond, Fredericksburg, and Washington, D.C. (Virginia Cooperative Extension, 1997); and between the Fall Line and Hampton Roads (Mostaghimi et al., 1995). Figures 2.1 and 2.2 illustrate the position of the James River Basin in Virginia. The James River watershed is approximately 6,676,453 acres in size (Chesapeake Bay Program, 2002).
Total farmland in the James River Basin is 1,181,671 acres, with 61 percent of the farmland in crop production primarily hay, corn, soybean, and small grains (Mostaghimi et al., 1995). Of the James River Basin farmers, 69 percent raise cattle for beef, 12 percent raise horses, and 12 percent run either a dairy or poultry operation.
Receiving the highest nitrogen loadings of any river in Virginia, the ecosystem health of the James River, as well as the Chesapeake Bay are in jeopardy (Chesapeake Bay Program, 2002). As shown in table 2.1, agriculture is the leading source of nutrients to the Chesapeake Bay (Novotny and Olem, 1994).
The Commonwealth of Virginia is divided into five geological areas known as physiographic provinces (Virginia Cooperative Extension, 1997). Each province is distinct and its particular set of characteristics influence water flow, attenuation of water, and ground and surface water contamination. Each physiographic province has unique soil, geological and geographical attributes. Soil type and geology are important features to consider when determining appropriate BMPs to combat agricultural pollution. The changing characteristics across the state pose significant challenges in assessing the appropriateness and quality of BMPs. For example, consider two identically designed, implemented, and maintained animal waste storage lagoons in different physiographic provinces. The first lagoon is sited in a province with a relatively high water table and soils susceptible to leaching, and therefore poses a higher environmental risk than the second lagoon located in an area with a greater distance to groundwater and soils not susceptible to leaching. This is a major issue because leaching from animal waste storage lagoons is a potential threat to groundwater quality. Another example involves the selection of appropriate plant species and planting dates for filter strips and cover crops across different physiographic provinces.
The James crosses four physiographic provinces. Figure 2.3 depicts the position of the physiographic provinces in Virginia. Most westward is the Valley and Ridge province (Virginia Cooperative Extension, 1997). Limestone, dolomite, shale, and sandstone dominate this region. Some of the most productive aquifers in the state of Virginia are found in this province, especially in the lowlands. The predominantly limestone formations of the Shenandoah Valley are largely responsible for the province’s high production aquifers. Conversely, the sandstone and shale of the ridges and uplands produce little water. The terrain of this province is primarily karst, with a high susceptibility to pollution. In karst areas, groundwater recharge in the form of streams and surface runoff enters caves and sinkholes, bypassing soil infiltration that may assimilate pollutants.
Moving eastward, the next province is the Blue Ridge, containing the highest elevations in the state (Virginia Cooperative Extension, 1997). Granite, gneiss, and marble are the dominant rock types. Thin soil and weathered rock overlying bedrock is characteristic of this steep terrain. The eastern section of the Blue Ridge is mostly igneous and metamorphic rocks while the western Blue Ridge is comprised of sedimentary rock. Rapid surface runoff allows for little groundwater recharge. Water is held in joints, fractures, and faults in the hard rock formations. Water quality is generally good in this province but groundwater extraction is limited to domestic wells and springs.
The Piedmont Plateau is the physiographic province that extends from the Fall Line west to the Blue Ridge Mountains (Virginia Cooperative Extension, 1997). This is the largest province in the state, with mostly hard, crystalline igneous and metamorphic rocks and bedrock covered by saprolite. In the western Piedmont, fractures and faults store the most water. A diverse subsurface geology is present, creating large ranges in groundwater quality and well production.
The Coastal Plain extends from the East Coast of Virginia inland about 185 kilometers (Virginia Cooperative Extension, 1997). Sand, gravel, clay and shell rock is mostly found in these unconsolidated deposits. This province stores the most groundwater in the state, but also uses about one-half of the state’s groundwater resources.
Nonpoint Source Pollution
Nonpoint source (NPS) pollution is defined legally as any pollution not originating from a statutory point source (Novotny and Olem, 1994). A point source pollutant enters a receiving water body at a single identifiable point location or multiple identifiable point locations; a NPS pollutant has an unidentifiable point of entry into the water body. Nonpoint source pollution can originate from urban settings, construction sites, and agricultural production. The EPA has identified agriculture as a significant source of NPS pollution in the United States (EPA, 1997). Agricultural sources of NPS pollution are return flow from irrigation, agricultural runoff and infiltration, silvicultural runoff and infiltration, runoff from pastures, runoff from rangelands, and wet and dry atmospheric deposition (Novotny and Olem, 1994). Agricultural NPS pollution accounts for 70 percent of impaired waters in the United States (EPA, 1999). The EPA estimates that 49 percent of lakes and 27 percent of estuarine square kilometers are classified as impaired due to agricultural nonpoint sources of pollution. The number two priority of the U.S. Department of Agriculture (USDA) is NPS pollution control under the National Program for Soil and Water Conservation (Gomez, 1995).
Soil type, topography, prior and current moisture conditions, type of crop and cropping method, and animal production management determine the concentration and volume of NPS pollution. Water transports natural and human-induced pollutants. Unlike point source pollution, which is most severe in low-flow drought conditions, NPS pollution is generally worst in the high-flow conditions associated with rainfall and snowmelt runoff events (Novotny and Olem, 1994).
Hydrologic factors are significant in NPS pollution considerations. The nature and amount of NPS pollution depends on many climatic variables, but precipitation is the most important. Soil detachment, disturbance, and loss are directly related to raindrop size and velocity (Novotny and Olem, 1994). Rainfall intensity also affects other hydrologic processes, such as infiltration and overland runoff rates. Interception, the presence of vegetation or artificial surfaces that slows or reroutes precipitation, can help prevent NPS pollution by diminishing soil disturbance.
Surface retention is the fraction of water that is not intercepted but is stored in depressions on the land surface (Novotny and Olem, 1994). Once in storage, water can evaporate, infiltrate, or if depression boundaries rupture the water can add to surface runoff and potentially contribute to NPS pollution. Infiltration is the movement of water through the air-soil surface interface and into the soil profile. Water that infiltrates the soil can be filtered by the soil particles on its way to groundwater, reducing the potential for NPS contamination. Infiltrated water is no longer at risk for becoming surface runoff, but may become interflow and resurface later in the watershed. Hydrologic factors differ across the physiographic provinces, impacting comparable BMPs in different ways.
There are four principal agricultural NPS pollutants—sediment, nutrients, pesticides, and organic matter. Best management practices target these pollutants to reduce the generation, transport, and delivery of the pollutants to water bodies where they make cause damage.
Sediment, by volume, is the largest agricultural pollutant (Cox, 1979). Sediment discharged to receiving water bodies can smother bottom-dwelling organisms, hinder aquatic reproduction, reduce light penetration and therefore photosynthesis, transport and mask other pollutants, and obstruct streams and lakes. Four billion tons of sediment enters waterways each year with about half resulting from natural processes and half from human activity (Novotny and Olem, 1994).
Nitrogen, phosphorus, and potassium are nutrients resulting from fertilizer, animal waste production, and surface runoff as represented in table 2.2. Rapid growth of aquatic vegetation, ecological imbalances, and depressed dissolved oxygen levels are effects of nutrient NPS pollution on natural systems (Cox, 1979). Eutrophication, the “death” of water bodies, is caused by nitrogen and phosphorus loadings (EPA 1999). While nitrogen is often the nutrient blamed for eutrophication, phosphorus losses that may not be agronomically significant can contribute substantially to eutrophication (Johengen et al., 1989). Oxygen depravation in water bodies is also caused by nitrogen and phosphorus, resulting in hypoxia and possible Pfiesteria piscicida blooms. Nutrient loadings are also one of the leading causes of taste and odor problems of potable water. An excessive nitrogen level in drinking water supplies is a health hazard due to methemoglobinemia, also known as “blue baby syndrome.” Methemoglobinemia is a condition where heightened nitrogen levels reduce the oxygen carrying capacity of blood, causing brain damage. Methemoglobinemia can be fatal in infants. The drinking water standard for nitrate-nitrogen is 10 mg/L (Hay et al., 1998).
CHAPTER 1 – INTRODUCTION
1.1 Problem Statement
CHAPTER 2 – LITERATURE REVIEW
2.1 James River
2.2 Nonpoint Source Pollution
2.3 Agricultural Best Management Practices
2.5 Assessing Best Management Practices
CHAPTER 3 – MATERIALS AND METHODS.
3.1 Best Management Practices Selected for Assessment Tool Development
3.2 Tool Development
3.3 Experimental Design
3.4 Site Visits
3.5 Statistical Analysis
CHAPTER 4 – RESULTS AND DISCUSSION
4.1 Assessment Tool
4.2 Quality Scoring
4.3 Statistical Analyses
4.4 Individual Best Management Practice Results and Discussion
4.5 Indicator Best Management Practice Category Results and Discussion
4.6 Cost-share Inferences
4.7 Age of Practice Effects on Best Management Quality
4.8 Farm Size Effects on Best Management Practice Quality.
4.9 Soil and Water Conservation District Effects on Best Management Practice Quality
CHAPTER 5 – CONCLUSIONS
5.1 Assessment Tool Development.
5.2 Factors Influencing Best Management Practice Quality.
5.3 Recommendations for Future Research
GET THE COMPLETE PROJECT
AN ASSESSMENT OF THE QUALITY OF AGRICULTURAL BEST MANAGEMENT PRACTICES IN THE JAMES RIVER BASIN OF VIRGINIA