Each point is one basin (WBD HUC4), over its HUC8s that lie mostly in Texas: its network flow paths in NHDPlus Version 2.1 (across) and in NHDPlus HR (up), filled with canals and ditches in both counts, hollow without them. On the line, the two would be equal. Ringed: the two datasets' areas for this basin differ by more than 5 %: Galveston Bay-San Jacinto, Brazos Headwaters, Lower Brazos, Upper Colorado, Lower Colorado-San Bernard Coastal, Central Texas Coastal, Rio Grande Closed Basins, Lower Pecos and Rio Grande-Falcon.

In the 11 Texas basins where the two datasets cover the same land (areas within 5 %), NHDPlus HR maps 3.0 times the network flow paths of NHDPlus V2.1.

In the same 11 basins, NHDPlus HR divides the land into about 766,000 catchments, where NHDPlus V2.1 has about 49,000.

Explore each basin

Neches River Basin

Our model: Upper Neches · USGS 08032000 (Neches River near Neches)

Trinity River Basin

Our model: Chambers · USGS 08063800 (Waxahachie Creek near Bardwell)

Red-Washita River Basin

Our models: Southern Beaver · USGS 07312200 (Beaver Creek near Electra); Little Wichita · USGS 07315200 (East Fork Little Wichita River near Henrietta)

Lower Colorado-San Bernard Coastal

Our model: South Concho · USGS 08131400 (Pecan Creek near San Angelo)

Central Texas Coastal

Our models: Upper San Antonio · USGS 08178800 (Salado Creek at Loop 13, San Antonio); Cibolo · USGS 08185000 (Cibolo Creek at Selma)

Nueces-Southwestern Texas Coastal

Our model: Upper Frio · USGS 08195000 (Frio River at Concan)

A model of your Texas watershed

We build a SWAT+ model for a USGS stream gauge in Texas, from national data. You download it as files you open in SWAT+ Editor and run, and you keep the files.

Texas programmes, groundwater, PFAS data and sources

Of the 169 HUC8s that lie mostly in Texas, one (12110203) is not carried by NHDPlus Version 2.1 and is left out of these figures.

Groundwater

MODFLOW 6 groundwater models are offered in Michigan Lower Peninsula, Indiana, Minnesota, Ohio, Wisconsin. Texas is not among them.

For context, the Texas Water Development Board publishes its own groundwater models: its northern Gulf Coast Groundwater Availability Model (v4.1, released January 2026) is a MODFLOW 6 model with six layers, calibrated from 1896 to 2018.

PFAS data in Texas

1,589 public PFAS monitoring stations in Texas, from 6 sources (read 14 October 2026).

EPA UCMR 5 (public water systems)	1,153 stations
EPA UCMR 3 (public water systems)	387 stations
Water Quality Portal	26 stations
DoD Fort Cavazos (formerly Fort Hood) PA/SI: groundwater wells	14 stations
EPA NRSA fish tissue	6 stations
DoD ASF Conroe	3 stations

Measured soil PFAS: 1,698 records from 7 agency sources in Texas, on the National PFAS Soil Inventory (read 14 October 2026).

Fort Bliss PFAS Preliminary Assessment / Site Inspection	515 records
Fort Cavazos (formerly Fort Hood), Army PFAS PA/SI, Table 7-1: 77 soil samples, located at the installation	385 records
JBSA Randolph AFFF Site Inspection (2018)	340 records
Lone Star Army Ammunition Plant	312 records
JBSA Lackland AFB Site Inspection	115 records
ASF Conroe PFAS PA/SI	30 records
Dallas County Superfund site, EPA SEMS	1 record

No Texas agency publishes PFAS data in a form we can ingest: TCEQ's surface-water data hold no PFAS parameter, and the Texas Water Development Board's groundwater database lists none among its 688 parameters.

The data a Texas model is built from

NHDPlus High Resolution streams and catchments, USGS 3DEP elevation, gSSURGO soils, NLCD land cover, PRISM climate, and USGS stream gauges.

For groundwater, Texas already has 33 Groundwater Availability Model pages at the Texas Water Development Board, which freely grants permission to copy and distribute its materials; surface-water availability in Texas planning comes from TCEQ's Water Availability Models. A SWAT+ model complements them; it does not replace them.

The work Texas water modeling serves

Regional water planning. 16 regional water planning groups (A to P) write the plans the state water plan is built from; the 2031 Initially Prepared Plans are due 4 March 2030. The plans must use TCEQ's Water Availability Models for surface water and TWDB's Groundwater Availability Models for groundwater. Sources: TWDB · 2031 schedule (PDF) · Exhibit C guidelines (PDF) · FAQ (31 TAC 357.32(c))

Regional flood planning. 15 regional flood planning groups; their plans are due 10 January 2028, and the scope of work asks for hydrologic and hydraulic models and Flood Management Evaluations. Sources: TWDB · Scope of work (PDF)

Flood Infrastructure Fund. At least $312.4 million in grants and zero-interest loans for 2026-27; Flood Management Evaluations, including hydrologic and hydraulic studies, are eligible only when a regional flood plan recommends them. Sources: TWDB · SFY 2026-27 Intended Use Plan (PDF)

Water quality. TCEQ total maximum daily loads and their implementation plans, and watershed protection plans under TCEQ and the Texas State Soil and Water Conservation Board (Clean Water Act section 319(h)). Modeling for a Texas watershed protection plan · Source

Groundwater conservation. 98 groundwater conservation districts in 16 groundwater management areas; final desired future conditions are due 5 January 2027, and Groundwater Availability Models turn them into modeled available groundwater. Sources: District facts · Management areas · Joint planning

The Edwards Aquifer. The Edwards Aquifer Authority's regional groundwater model is built in MODFLOW 2000, and its Habitat Conservation Plan includes springflow protection measures. Source

Land subsidence. The Harris-Galveston and Fort Bend subsidence districts regulate groundwater withdrawal; the Harris-Galveston district developed the GULF-2023 model with the USGS and the Texas Water Development Board. Source

SWAT in Texas

The SWAT model's website is hosted at Texas A&M (swat.tamu.edu), and Texas A&M AgriLife's Blackland Research and Extension Center in Temple lists SWAT among the models it has deployed worldwide.