Water and Salt Transfers in an Irrigation District

Water quality and volume of supply water and of return flow were observed for 3 yr in a 57,400-ha irrigation district in southern Alberta. Water passing directly from canals to surface drains and runoff from flood irrigation were estimated at about 87% of the total return flow. Due to dilution of saline ground water by better quality water, most of the water quality objectives set by the provincial environment authority were met in the return flow. The total phosphorus was directly related to sediment eroding from drain banks and bottoms. The salt balance index (salt outflow/inflow) was greater than 1.0 for only one block of the district for 2 of the 3 yr. The index was lower than that of most irrigation districts in North America; probably because an extensive subsurface drain network is lacking.