Inside a watershed model: five Texas SWAT+ examples

What is actually inside a watershed model? Here are five, from across Texas, and you can explore every one of them on the map.

A SWAT+ model splits a basin into pieces it can compute: channels that carry water, and hydrologic response units, patches that share a soil, a land cover and a slope. Each one is a small water budget, run day by day.

Pecan Creek, near San Angelo. 207 square kilometers, 270 channels, about 2,100 response units. Waxahachie Creek, near Bardwell, south of Dallas. 451 square kilometers, almost 1,200 channels, and 285 water bodies the model carries.

Salado Creek, gauged at Loop 13 in San Antonio. 471 square kilometers, 617 channels, about 12,000 response units.

Beaver Creek, near Electra, close to the Red River. 1,669 square kilometers, 4,450 channels, almost 35,000 response units, and 870 water bodies. And the Neches River, near Neches, in East Texas, the biggest of the five: 2,913 square kilometers, more than 11,000 channels, almost 117,000 response units, and nearly 2,000 water bodies.

These are uncalibrated models. The structure is built from national data, and each one runs a full year, 2024. Matching a model to what its gauge measured is a separate step, calibration, and these, as published, are not calibrated.

So what is inside a watershed model? Thousands of small, linked water budgets, built for one gauge. Five of them in Texas are on the SWATGenX map. Explore them there, and sign in to download them.