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Indicator Type: Environmental Pressure
In much of southern Alberta, there is typically not enough rainfall and moisture to naturally sustain agricultural crops. However, there is abundant sunshine and heat that can grow many different crops if water is not a limiting factor. Early in the settlement of Alberta , it was recognized that agriculture would not be successful in the southern region without an abundant and assured supply of water in order to irrigate the fields. Irrigation Districts were organized and granted water licenses to divert large quantities of water from the tributaries of the South Saskatchewan River, primarily the Oldman (St. Mary, Waterton and Belly) and Bow Rivers.
This indicator depicts the reported amount of water diverted over time by Irrigation Districts.
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Trend: Generally stable with large year-to-year variability
Last Updated: October 2005
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What does the indicator show?
Water requirements for irrigation vary from year to year, as shown above. In general, the greatest factor driving demand is what the weather is like for each particular growing season – although the type of crops being grown also influences demand. Irrigation diversions are driven by the relationship between supply and demand between wetter and drier years. For example, demand for irrigation water will be highest when it is a relatively hot and dry year, but those are also typically the years when the available supply of water tends to be less. In wetter years, there is generally more water available to divert but crops may not need as much irrigation water. This balance between supply and demand can be partially addressed by growing fewer water-intensive crops in drier years.
Note that total allocations permitted are higher than the amounts historically diverted. Allocations do not guarantee water supply; rather they guarantee the right to take water, if sufficient water is available.
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Why is this indicator important?
Irrigation for agriculture is the largest user of water in Alberta. In 2004, irrigation accounted for over 43% of allocated surface water, or more than 4 billion cubic metres. It represents almost 75% of all water allocated in the South Saskatchewan River Basin. The thirteen organized Irrigation Districts collectively represent the largest amount of water allocated for a specific purpose in Alberta at over 3.5 billion m³. The four largest districts account for 83% of total diversions, with two more accounting for an additional 12%. Seven remaining small districts account for the other 5%.
Nearly all uses of water result in some water that is not returned back to the local ecosystem. With irrigation, the majority of water that is applied to crops is taken up by the plants for g rowth, or evaporated. There is also some amount of water that is never used for irrigation itself, but is needed to maintain the minimum depth of water in canals and reservoirs in order to transport irrigation water through the system; therefore some of this water ends up as return flow back into other creeks and rivers.
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What actions are being taken?
Irrigation Districts are constantly evaluating their infrastructure and irrigation practices to minimize water losses (through seepage and evaporation) and maximize the area that can be irrigated. Improving efficiencies mean that less water is needed to produce the same amount of crop, or, that more area can be irrigated with the same amount of water. The South Saskatchewan Basin Water Allocation Regulation recognized limits to the expansion of irrigated areas given that many basins have already been fully allocated or are approaching supply limitations. Phase Two of the South Saskatchewan River Basin Water Management Plan, currently underway, seeks to address collectively amongst stakeholders in the basin the ecological issues that result from large-scale diversions of rivers, while balancing against socio-economic considerations.
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Links to additional information
Irrigation Districts In Alberta
Alberta Agriculture, Food and Rural Development – Irrigation Branch
South Saskatchewan River Basin Water Management Plan
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Feedback
E-mail the SOE Coordinator: SOE.Coordinator@gov.ab.ca or complete this short on-line questionnaire to provide your feedback: http://www.zoomerang.com/
survey.zgi?p=WEB224DW6P3E2K.
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