Patterns of Irrigated Agricultural Land Conversion in a Western U.S. Watershed: Implications for Landscape-Level Water Management and Land-Use Planning

Abstract

In irrigated agricultural landscapes, land-use conversion may have landscape-level social, hydrological, and ecological effects. We used geographic information systems (GIS) and interviews to analyze development effects on irrigation in the Henry's Fork Watershed, Idaho. Farmers developed irrigation there in the 19th century, and incidental recharge from canal seepage and flood irrigation raised groundwater levels and expanded wetlands. Cohesive culture in agricultural communities sustained irrigation systems until amenity-driven demographic shifts beginning in the 1970s led to development approved by local governments with land-use planning but no water-management authority. Although only 5% of irrigated land has been converted, development has fragmented irrigated landscapes and made canal-system operation more difficult, potentially reducing groundwater levels, wetland extent, and return flows critical to downstream irrigators and fish and wildlife. We discuss future scenarios, highlighting the need for increased communication among local and state governments regarding land use and water management in irrigated landscapes across the West.

Keywords:

• groundwater
• irrigated agriculture
• land-use conversion
• water management
• western United States

Acknowledgments

At the time of this research, Rob Van Kirk was with the Department of Mathematics at Humboldt State University, Arcata, CA. He is currently affiliated with Henry's Fork Foundation, Ashton, ID.