Surface Water Supply Index (SWSI)

A Surface Water Supply Index (SWSI) is a predictive indicator of the surface water available in a basin compared to historic supply. The SWSI is calculated by summing the two major sources of irrigation water supply; reservoir carryover and spring and summer streamflow runoff. These two sources are analyzed together when determining the total surface water supply available for the season.

Monthly SWSI Products

Statewide Summary Table:   Select monthJanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctober  

Individual Basin Tables:

        Select Month JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctober   Select Basin Bear RiverBig LostBig Wood above HaileyBig WoodBoiseBruneauClearwaterHenrys ForkLittle LostLittle WoodPanhandleOakleyOwyheePayetteSalmon Falls above JackpotSalmon Falls CreekSalmonSnake near HeiseSpokaneTetonWeiser  

 

1981 to Present Streamflow and Reservoir Graphs:

        Select Month JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptember   Select Basin Bear RiverBig LostBig Wood above HaileyBig WoodBoiseBruneauClearwaterHenrys ForkLittle LostLittle WoodPanhandleOakleyOwyheePayetteSalmon Falls above JackpotSalmon Falls CreekSalmonSnake near HeiseSpokaneTetonWeiser  

 

Period of Record Streamflow and Reservoir Graphs:

        Select Month JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptember   Select Basin Bear RiverBig LostBig Wood above HaileyBig WoodBoiseBruneauClearwaterHenrys ForkLittle LostLittle WoodPanhandleOakleyOwyheePayetteSalmon Falls above JackpotSalmon Falls CreekSalmonSnake near HeiseSpokaneTetonWeiser  

Flow Trend Graphs

Individual Flow Trend Graphs:   Select BasinBear RiverBig LostBig Wood above HaileyBig WoodBoiseBruneauClearwaterLittle LostLittle WoodOakleyOwyheePayetteSalmon Falls above JackpotSalmon FallsSalmonSnake HeiseSpokaneTetonWeiser  

 

Surface Water Irrigation Outlook

• 2019 Streamflow Needed for Adequate Irrigation Supply
• 2019 Salmon Falls Reservoir Storage Allotment: Jan | Feb | Mar | Apr | May
• 2014 Surface Irrigation Shortage Outlook based on 5 Exceedance Forecasts

Drought Related Links

• US Drought Monitor - Map of Current Drought Status (Updated weekly)
• Snowpack/Drought Monitor Weekly Update Reports (Updated weekly)
• US Seasonal Drought Outlook - Map (Updated monthly)