Water Sources, Hydrology, and Source Water Protection
What the candidate must know
Texas source waters include surface water (rivers, reservoirs, lakes) and groundwater (aquifers). Candidates should understand watershed hydrology basics - precipitation, runoff, infiltration, evaporation, and how drought and flood cycles affect raw water quality and quantity. Know the difference between a watershed (drainage area) and a recharge zone, and understand how land use affects turbidity, nutrients, and pathogen loading.
Concepts to master
- Surface water vs. groundwater characteristics: turbidity, temperature variation, mineral content, and susceptibility to contamination.
- Source Water Protection: wellhead protection areas, watershed protection plans, and the role of the Texas Source Water Assessment Program.
- Total Maximum Daily Load (TMDL) and impaired water bodies under Clean Water Act Section 303(d).
- The hydrologic cycle and how reservoir stratification affects raw water quality (turnover, anoxia in the hypolimnion).
- Drought contingency and water conservation planning requirements.
Traps in questions
A common trap is assuming groundwater is always cleaner; questions may describe an aquifer with high hardness, iron, or arsenic. Another trap is confusing a watershed with a wellhead protection area, or confusing TMDL with a discharge permit limit.
Worked example / rule of thumb
Rule of thumb: surface water quality varies with season and storm events; groundwater quality is more stable but geologically influenced. If a question describes sudden turbidity spikes after rain, think surface water and watershed runoff.