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Sulphur basin · North East Texas · North Central
TWDB reading Sep 8, 2026
USGS 07342495 — Jim L. Chapman Lk nr Cooper, TX
Extrapolated from the past 60 days
Falling roughly 610 acre-feet per day. At that rate the conservation pool would be exhausted in about 314 days.
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 Hopkins County, Sep 1, 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 33 years of record for this date
At 80%, Cooper (Chapman) Lake is below normal for this date, lower than 70% of years on record. It was last this low in 2022.
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.
Inflow minus release at the two gages above. This is not a closed water balance — ungaged tributaries, rain on the lake, evaporation, and direct withdrawals are not measured here, so it will not reconcile exactly with the day-to-day storage change.
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.
Official NWS stage/flow forecasts for gauges around this reservoir
Issued by the NWS National Water Prediction Service, typically a few times a day, about five days out. A river forecast is not a lake-level forecast: releases are managed, and the gauges can sit well away from the dam.