Lower Little Bow River Watershed
The 55,664-hectare Lower Little Bow River Watershed is located within the Oldman River Basin in southwest Alberta. The Lower Little Bow Watershed Evaluation of Beneficial Management Practices (WEBs) project focused on a micro-watershed (2,565 hectares) north of Lethbridge. See map.
Land use in the Lower Little Bow River Watershed includes a wide range of agricultural activities and intensities such as cow-calf operations on native range, dryland farming, intensive irrigated row crop farming, and intensive livestock operations. The study area incorporated 13 farms.
Surficial geology consists mainly of glacial till. The upland terrain is undulating with slopes between two to five percent. Soils in the watershed are primarily Dark Brown Chernozems, with some Regosols adjacent to the river.
The climate is dominated by strong chinook winds. Average annual precipitation is about 386 millimetres, of which approximately one-third falls as snow. Flows in the Lower Little Bow River are controlled by irrigation reservoirs and runoff often occurs from fall irrigation. Nutrients from manure and fertilizers, and bacteria from manure, are believed to be impacting water quality in the Lower Little Bow River.
Considerable background information is available on this watershed, much of it collected under the Oldman River Basin Water Quality Initiative.
Since 1999, Alberta Agriculture and Rural Development (AARD) has quantified phosphorus, nitrogen, fecal coliforms and E. coli in surface runoff at 10 monitoring stations along the Lower Little Bow River. Runoff from a micro-watershed within the basin was studied by AARD from 2002 to 2005 as part of the provincial soil phosphorus limits study.
Five BMPs were studied within the Lower Little Bow River Watershed as follows:
- Cattle exclusion fencing, with the provision of an off-stream water supply
- The provision of off-stream water without fencing
- Manure management
- Buffer strips
- The conversion of cropland to forages (BMP evaluation discontinued in 2010)
The Streambank Fencing in Southern Alberta fact sheet discusses methods and findings from this evaluation.
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