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Water Resources Data System
Dept 3943
1000 E. University Ave.
Laramie, WY 82071

Ph (307) 766-6651
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Wyoming Surface Water Supply Index

The Surface Water Supply Index (SWSI) is computed using only surface water supplies for the drainage. The computation includes reservoir storage, if applicable, plus the forecast runoff. The index is purposely created to resemble the Palmer Drought Index, with normal conditions centered near zero. Adequate and excessive supply has a positive number and deficit water supply has a negative values. Soil moisture and forecast precipitation are not considered as such, but the forecast runoff may consider these values.