San Marcos HUC8 12100203
A 3,520 km² sub-basin of the Texas-Gulf region in TX. Drought coverage is from the US Drought Monitor (map of 2026-09-01); streamflow classes place each USGS gauge's latest reading against its own day-of-year record.
Health score
58
Moderate
Drought index
143
Moderate
Area in D2+
0%
0% exceptional (D4)
Gauges below normal
64%
of 11 reporting
Median flow
25%
p17 of record
Water assets
1,575
134 springs · 621 wells
USGS gauges (13)
- Blanco Rv at Fischer Store Rd nr Fischer, TX081709500 cfsp0 · much below normal
- Blanco Rv at Wimberley, TX081710006 cfsp8 · much below normal
- Jacobs Well Spg nr Wimberley, TX081709900 cfsp10 · below normal
- Blanco Rv nr Kyle, TX081713000 cfsp10 · below normal
- Blanco Rv at San Marcos, TX081713500 cfsp10 · below normal
- San Marcos Rv at San Marcos, TX0817050095 cfsp17 · below normal
- San Marcos Rv at Luling, TX0817200097 cfsp23 · below normal
- Blanco Rv at Halifax Rch nr Kyle, TX081712906 cfsp27 · normal
- San Marcos Rv nr Martindale, TX08171400126 cfsp33 · normal
- Plum Ck nr Luling, TX081730005 cfsp41 · normal
- Plum Ck at Lockhart, TX0817240016 cfsp97 · much above normal
- Little Blanco Rv at FM 32 nr Fischer, TX081708900 cfsno long-term record
- Blanco Rv at Valley View Rd nr Fischer, TX081709050 cfsno long-term record
Recent conditions
| Date | DSCI | D2+ % | Gauges low | Flow pct |
|---|---|---|---|---|
| 2026-09-07 | 143 | 0 | 7/11 | p17 |
Top water assets
- 74Trinity Aquifer — Hill Country Regionaquifer
- 66Lower Plum Creek Ws Scs Site 29 Damreservoir
- 66York Creek Ws Scs Site 4 Damreservoir
- 66York Creek Ws Scs Site 5 Damreservoir
- 66Pierce Lake Damreservoir
- 66Plum Creek Ws Scs Site 20 Damreservoir
- 66Plum Creek Ws Scs Site 21 Damreservoir
- 66York Creek Ws Scs Site 3 Damreservoir
- 66Lower Plum Creek Ws Scs Site 23 Damreservoir
- 66Plum Creek Ws Scs Site 16 Damreservoir