| | Livestock practices that can cause impacts to water quality include both intensive and non-intensive operations. Intensive operations include feedlots (>500 head of cattle), dairies and wintering sites while non-intensive operations include pasture, cow-calf operations and watering sites for cattle. Waste management and disposal can also impact water quality. Livestock density is not the only factor affecting water quality as siting and management are also important considerations. Water quality parameters related to livestock production include nutrients (nitrogen and phosphorus), microorganisms (e.g. bacteria, faecal coliforms, Cryptosporidium, Giardia) and organic material such as livestock wastes. Water quality concerns include impacts on receiving streams and aquatic life, and reuse of the water downstream for agricultural, recreational and drinking water purposes.
Intensive operations
Intensive livestock operations such as cattle feedlots and overwintering sites can have a large impact on water quality. Water quality impacts are usually from high densities of animals that can generate large quantities of animal waste. Localized concentration of animal waste is considered a point source of pollution for surface or ground water. Mismanagement or improper storage of animal wastes can contaminate water sources.
Manure mismanagement can have devastating impacts on stream ecosystems. Ackerman and Taylor (1995) identified intensive agricultural livestock operations as point sources of pollution to streams. For example, a swine operation in Illinois was linked to ongoing fish kills in an adjacent stream. The open-front facility lacked any waste collection structure to collect nutrient-rich runoff. Manure drained directly from the feedlot into the adjacent stream. Dissolved oxygen, phosphorus and ammonia concentrations exceeded Illinois water quality standards.
In addition to manure mismanagement, poor manure holding structures or human error can cause surface water contamination. For instance, a 500-head cattle feedlot was responsible for an extensive fish kill along more than 8 miles (12.9 km) of stream (Ackerman and Taylor 1995). Dissolved oxygen and ammonia concentrations exceeded water quality standards. The feedlot was designed to drain manure into a waste collection pit that was periodically pumped to an above-ground storage structure. A valve on the transfer pump was inadvertently left open allowing manure to backflow into the collection pit that overflowed and drained into an adjacent stream. Likewise, an improperly constructed earthen manure storage facility for a swine farrow-to-finish operation caused the contamination of the Fitzgerald Drain, part of Medway Creek near London, Ontario, that resulted in a fish kill (UTRCA 1994).
Elevated faecal coliform bacteria concentrations in surface water can be linked to intensive livestock operations. Mean faecal coliform concentrations exceeded the USEPA permissible level for raw water supply in a stream receiving effluent (point source) from a 200-cow dairy operation (Hollon et al. 1982).
A study in North Carolina investigated nutrient runoff from animal waste as the source of surface water contamination that resulted in large blue-green algal blooms, fish kills and declining commercial and sport fisheries. Duda and Finan (1983) demonstrated that higher concentrations of nutrients occurred in agricultural watersheds with extensive artificial drainage and high livestock populations than in similar agricultural watersheds with low livestock densities.
Wintering grounds for cow-calf operations contain lower livestock densities than feedlots. However, higher livestock densities during the winter can cause a localized accumulation of livestock waste that can be easily transported to surface water in spring runoff. Chichester et al. (1979) found that winter feeding caused a high degree of soil and plant cover disturbance and an increase in surface runoff and erosion as compared with the pastures grazed only in the summer. Feeding cattle in a winter feeding area increased runoff and caused more chemical movement (i.e. total N, total P, organic C) as compared with the pastures only grazed in the summer. Evidence also suggests that cattle wintering areas may cause other related water quality problems. Winter feeding areas have shown increases in nutrients and soluble salts which can lead to development of problems with colour, taste, odour, and biochemical oxygen demand (BOD). These areas can also directly produce odours from decay products and high bacteria and pathogen loadings from animal waste.
Waste handling
Manure mismanagement can cause pollution of surface water and ground water. Poor manure management practices include the following: manure spreading on frozen or compacted soils, manure application in excess of crop requirements and improper storage facilities. For example, Ackerman and Taylor (1995) found that the mismanagement of liquid swine waste from a 500-head sow, farrow-to-finish swine facility in Illinois caused severe degradation in water quality in a local pond. The deterioration of water quality was linked to the spreading of liquid manure on frozen cropland. Spring runoff flushed the manure into the pond causing high ammonia concentrations and high biochemical oxygen demand that resulted in a fish kill.
The application of plant nutrients (nitrogen and phosphorus) in excess of crop demand can result in the contamination of surface and ground water. For example, in Delaware, Andres (1995) found nitrate contamination in ground water under cropland that received excessive applications of manure. Factors contributing to the nitrate contamination include: agricultural land use; flat topography; well-drained, highly permeable soils and aquifer characteristics in this region. However, Andres (1995) found that nitrate contamination was more severe in areas with intensive animal production than elsewhere. Approximately one-third of the wells had nitrate concentrations in excess of the drinking water standards.
Similarly, inappropriate fertilization practices may cause surface water contamination following snowmelt. Gangbazo et al. (1995) found high ammonia losses and water contamination when hog manure was applied in the fall as opposed to the spring. Ammonia concentrations exceeded the acceptable level for raw drinking water. In addition, there was increased public health risk to drinking water supplies since ammonia can react with chlorine to produce chloramines during the water treatment process. Chloramines are less effective disinfectants. Taste and odour problems may also result from high ammonia concentrations. Microorganisms such as Cryptosporidium or Giardia can also contaminate water supplies. For example, Edwards (1993) reported that an outbreak of cryptosporidiosis in Milwaukee was linked to heavy rains and spring runoff in the watershed that supplied the city's drinking water. An estimated 370,000 city residents became ill as a result of drinking contaminated water. Cryptosporidium are common in mammals, especially calves and birds. They are resistant to chlorine treatment; however, they are removed through proper water filtration treatment. Although the source of the contaminated water in Milwaukee was not specifically determined, snowmelt and rainstorms can wash manure into rivers. The outbreak was linked to a combination of spring runoff, which over-stressed the water treatment system, and a change in the water treatment process.
Grazing
Although cow-calf operations have lower livestock densities than feedlots, grazing and cow-calf operations can potentially contaminate surface water. Robbins (1979) found that runoff is proportionately higher from a heavily grazed watershed than moderately or lightly grazed watersheds. High runoff is due to the compaction of the soil from cattle's hooves and grazing practices. Water contamination from grazing operations includes increased sediment and bacterial counts in runoff.
Grazing practices can cause surface water contamination. For instance, Doran and Linn (1979) found bacteria concentrations in runoff from both grazed and ungrazed pastures in Nebraska exceeded water quality standards for primary contact recreation and drinking water supplies. Cattle contributed more bacteria in runoff when a bacterial indicator was used to determine the relative contributions between cattle and wildlife. Additionally, Schepers and Francis (1982) conducted a three-year runoff study from a 32.5 ha cow-calf pasture in Nebraska. They evaluated nutrient loads in runoff when cattle were grazing or not grazing during a runoff event. They found that livestock influenced nitrate, soluble phosphorus, chemical oxygen demand and chloride concentrations in runoff. Dissolved solids and nutrients in runoff increased from 6% to 78% when livestock were grazing.
Watering sites
Water access is an essential part of livestock management. Watering practices that can impact water quality include direct cattle access to waterways and destruction of riparian ecosystems through overgrazing. Direct access to water sources for cattle allows for direct deposition of wastes and increased erosion. Cattle can destroy riparian ecosystems through overgrazing and soil compaction from cattle's hooves. A healthy riparian zone is vital for maintaining a healthy stream ecosystem. A healthy riparian ecosystem is better able to buffer the destructive impacts of flood and drought.
An increase in stream biodiversity results from reduced grazing. For example, Kauffman and Krueger (1984) reported a 48 to 78% decrease in stream sediment loads when streams were protected from livestock grazing. In addition, they found greater streambank losses in grazed areas as compared to ungrazed areas (average channel width was 53 and 18.6 m for grazed and ungrazed areas, respectively).
Higher instream temperatures reduce the survival of some aquatic organisms. Livestock use can increase instream temperatures. For instance, Kauffman and Krueger (1984) reported a drop in average stream temperature from 24oC to 22oC after one year of livestock exclusion on a creek in Nebraska. Similarly, average stream temperatures were lowered by 7oC and daily fluctuations were lower (7oC as compared to 15oC) in an area that was rested for four years and then grazed only after August 1, versus an area grazed for the entire season (June 1 to October 15). In addition, healthy fish populations reflect a healthy instream environment. In five independent studies, fish production increased, on average 184%, in streams that reported minimal or no livestock use. Additionally, rough (non-sport) fish composed 88% of a fish population before relief from grazing and only 1% of the population after an eight-year rest.
Summary
Cropping and livestock practices can impact surface and ground water quality. Many studies have shown that water quality guidelines and standards have been exceeded as a result of agricultural activities. High concentrations of nutrients, pesticides, and sediment in runoff represent both an economic loss to the farmer and an environmental impact. Water quality can be improved by implementing proper best management practices (BMPs). Some of these BMPs have been evaluated at field and watershed scales in Alberta. For information click on the following project links:
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