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Colorado basin · Region F · Edwards Plateau
TWDB reading Jul 23, 2026
USGS 08123950 — E. V. Spence Res nr Robert Lee, TX
Extrapolated from the past 60 days
Falling roughly 40 acre-feet per day. At that rate the conservation pool would be exhausted in about 3.9 years.
A straight-line extrapolation, not a forecast. It assumes the recent rate continues unchanged, ignoring seasonality, rainfall and managed releases — and drawdown normally slows as a reservoir falls. Treat it as a severity signal, not a date.
US Drought Monitor for Coke County, Jul 21, 2026
Conditions in the county containing the dam. A reservoir is filled by a watershed that often reaches well beyond one county, and releases are managed, so local drought is context rather than an explanation of the level.
Nearest gaged reaches above and below the dam
How today compares with 58 years of record for this date
At 11%, E. V. Spence Reservoir is below normal for this date, lower than 74% of years on record. It was last this low in 2018.
Percentiles pool the ±3 days around today across every year on record, so “normal” means normal for this time of year. Conservation capacity is re-surveyed over time, so percent-full comparisons across decades are close but not exact.
Daily TWDB observations, with the normal range for each date
Normal range for the date (25th–75th percentile)Median year
Past 7 days, typically 15-minute readings. USGS elevations use a published datum that may differ slightly from the TWDB daily value above.
CoCoRaHS observers within 60 km of the dam
Rain measured near the dam, not across the watershed. A reservoir is fed by a catchment that can reach hundreds of kilometres upstream, so heavy local rain does not necessarily mean inflow — and a rising lake often reflects rain far from here. Readings are volunteer observations taken once each morning.