Follow the change. Keep the context.

Why did the lake level change?

Elevation alone cannot identify a cause. Rainfall, inflows, releases, withdrawals and evaporation can all affect a reservoir. We do not assign a cause from a change in elevation without separate, dated operating or hydrologic evidence. Follow the operating agency for a specific explanation.

Is a fall in feet the same as a fall in percent full?

No. Percent full describes storage relative to the source’s capacity definition. Reservoir shape determines how a change in height translates into volume. A one-foot fall does not equal a one-percentage-point fall. Read the elevation and storage guide.

Why is a comparison unavailable?

Both endpoint dates must exist once in the accepted series and contain valid numbers. We subtract exactly seven or thirty calendar days from the latest series date. We do not interpolate, substitute a nearby date or turn a missing value into zero.

Does a falling level mean a lake is unsafe or closed?

No access or safety conclusion follows from these differences. Ramps, shorelines and operational restrictions require separate current checks. Open the lake’s agency record and local access notices before making plans.

Why are tides and river gauges absent?

This report uses daily reservoir elevation history. Our tide pages show predictions, while river pages use instantaneous gauge observations. Mixing those with daily reservoir readings would produce misleading comparisons. Understand gauge height and discharge.

Method and reproducibility

For each source series: change = latest dated elevation − elevation on the exact baseline date. Differences are rounded to two decimal places after subtraction. TWDB series dates and CDEC daily series dates are preserved; they are not assumed to be synchronized instants. Agency revisions may change a subsequent report. The CSV preserves baseline, latest value, dates, source identity, source URL and retrieval time; save it with a download date when citing it.

Full measurement methodology · Source-checking checklist · Station directory