Water Use and Quality on the Prairies
The great need for water by agriculture is one of the reasons why water is in short supply on the prairies. The lack of water in the southern prairies contributed to the devastating experience of farmers in the drought area of the 1930s. Indeed, during the 1961 - 90 period, the average annual precipitation in Regina was 362 mm while the average evaporation rate was 1016 mm, resulting in a net deficit of 654 mm 1. This difference illustrates the need to conserve moisture supplies and reduce the evaporation rate through the application of technology. Furthermore, quality water constitutes only part of the supply available. On the other hand, agricultural operations can contribute to loss of quality in water. A further complicating factor is the unequal distribution of water in the prairie region. Consequently, water use and quality have become a major issue on the prairies with regard to the sustainability of agriculture in the region.
The low level of precipitation and its uneven distribution on the prairies in combination with evapotranspiration has made redistribution of the available supply of water of paramount importance. Redistribution may be accomplished by on-farm techniques to retain the precipitation that falls. More generally, water is drained from undesirable locations to others more desirable as well as transferred within basins and also between basins. The latter techniques decrease the impact of the variability of precipitation. Such redistribution activities are not without cost and may have an undesirable effect on the environment.
While ground water is the most abundant and widely distributed water source, the water quality, yield and dependability of the aquifers can vary considerably. Deep aquifers, while more resistant to drought, tend to have high treatment costs in order to make them potable. One of the first activities of PFRA following its inception in 1935 was to embark on construction of on-farm dugouts to capture any runoff for domestic and livestock use. Dugouts have been termed as an inelegant a collection of holes as ever designed by man. They did nothing aesthetically for the landscape. They were utilitarian in the extreme. Yet, if acceptance is a measure of worth, few more valuable projects were ever devised 2. PFRA projects also included stock watering dams and other on-farm water supply projects. To date, over 200,000 of such on-farm water projects have been completed through joint producer and PFRA action.
Comprehensive planning combined with coordination and sound water management are fundamental requirements for the development and maintenance of secure water supplies. Increased water use combined with occasional droughts have resulted in the failure of many surface sources and shallow water aquifers to provide sufficient water for farms and rural communities. As a result, within the prairies with the cooperation of PFRA virtually every major system has been modified by means of reservoirs so that the flow of water in peak times is made available for use in drought periods. Of the approximately 770 dams in the prairie provinces, 53 percent are in Saskatchewan, 40 percent in Alberta and 7 percent in Manitoba. The most monumental of these river projects is the Gardiner Dam on the Saskatchewan River at Outlook, Saskatchewan, which created Lake Diefenbaker 3. Even though the irrigation potential remains largely undeveloped, the benefit to cost ratio of this multi-use project generally exceeds one without the uncalculated benefit of the climate modification associated with such a large body of water 4. Originally proposed by Henry Hind in 1859, the dam was completed in 1968. There are an additional 19 major dams on rivers in the prairie region.
Irrigation has been shown to enable a form of sustainable agriculture to develop in an arid region, with a complementary output of products which can provide the basis for development of substantial value added industries. Economic stability is achieved following the development of a successful irrigation area. These benefits serve to offset public investments in the associated water management projects. It should be noted that the development of irrigation in Southern Alberta early in the 1900s enabled the area to escape the disastrous consequences of the "dust bowl" which developed further east on the prairies during the 1930s.
Irrigation accounts for approximately 88 percent of the total water used for agriculture. Irrigation is practised on about one million hectares of land in the brown and dark brown soil zones, the crops produced being primarily cereal grains. Recent droughts have stimulated interest in additional water management projects. Unless the water is wisely used soil salinity problems may be experienced. At the same time inter basin transfers can give rise to introduction of new species and to habitat loss for fish and wildlife.
Redistribution of water tends to be expensive. Use of public funds for this purpose is subject to increasing scrutiny. Questions arise as to whether use of these funds would return greater benefits if spent for other purposes. The net pay-off of most past irrigation projects has been positive. Many projects are multipurpose in nature providing water supplies for power generation, municipal use, recreation, and wildlife habitat as well as for agriculture.
Not only does the sustainability of agriculture have a water quantity requirement but also one of water quality. For human and livestock use, the quality requirements are quite stringent. For crops, levels of tolerance are somewhat higher. Even treated effluent from municipal sewage plants can be used to irrigate crops.
Agriculture itself can become a source of water pollution both on and off location. Local pollution sources include processing plants, and confined livestock operations. The primary pollutants are phosphorous, nitrogen and organic materials. Off-site pollution from agriculture includes phosphorous, nitrogen, pesticides and sedimentation of streams and lakes.
Water has and no doubt will continue to have a major impact on the sustainability of agriculture on the prairies. Snow management can add three centimeters of water for the production of the next crop 5. The additional water is of great value, particularly in the brown and dark brown soil zones where on average the amount available is inadequate. The additional water from snow management can often provide an alternative to summer fallow as a means to increase soil moisture. Adoption of water efficient cropping systems such as minimum tillage or zero tillage can also alleviate the moisture shortage in crop production. Control of weeds and use of fertilizer improve the efficiency with which the available moisture is used in the production of crops. All these activities point to the desirability of improved water management on the farm. Such management could overcome some of the need to summer fallow in the brown and dark brown soil zones for the purpose of storing water for the next crop.
It must be emphasized that sustainable agriculture on the prairies depends on an adequate supply of water. In the past, there was little outside competition for the available supply. However, competition is expected to increase as municipal demands rise along with the population and as demands from industry expand. In consequence, efficiency in the use of water will become mandatory. In this environment, water from off-farm sources can be expected to be only available at full cost, rendering most proposed additional water storage works for agricultural purposes uneconomical. In addition, greater scrutiny of the pollution of water by agricultural operations can be expected. On the other hand, increasing concern for the maintenance of wetlands for environmental purposes should promote the sustainability of agriculture.
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