Lecture ERS 482/682 (Fall 2002) TMDL Assessment ERS 482/682 Small Watershed Hydrology

Lecture ERS 482/682 (Fall 2002) Definitions TMDL: total maximum daily load of a pollutant that achieves compliance with a water quality standard TMDL process: plan to develop and implement a TMDL pollutant: substance added by humans or human activities; also habitat destruction, hydrologic modification, etc. pollution: man-made or man-induced alteration of chemical, physical, biological, and radiological integrity of water

Lecture ERS 482/682 (Fall 2002) TMDL program Originates from Section 303d of the Clean Water Act: –Makes it the responsibility of the states to assess whether or not ambient water quality standards are being met for individual waterbodies –If the ambient water quality standards are not being met, a water quality management program must be implemented to achieve the standards water quality in the waterbody

Lecture ERS 482/682 (Fall 2002) ambient water quality effluent water quality Point source controls Point and nonpoint source controls EASY NOT SO EASY

Lecture ERS 482/682 (Fall 2002) Nonpoint sources Examples: –Runoff from urban areas, construction sites, golf courses, etc. –Atmospheric deposition –Groundwater seepage –Snowmelt We need to know about watershed hydrology!

Lecture ERS 482/682 (Fall 2002) TMDL program States must identify waters not meeting ambient water quality standards –Define pollutants –Define sources –Establish TMDLs necessary to secure the standards –Allocate responsibility for reducing pollutant releases 1992 amendment to TMDL regulations –States must submit lists of impaired water bodies every two years

Lecture ERS 482/682 (Fall 2002) TMDL program Reports are at: Nevada’s TMDL report is at

Lecture ERS 482/682 (Fall 2002) TMDL process All waters Determine designated use/ standard Listing PlanningImplementation NRC (2002) Figure 1-1 Every two years

Lecture ERS 482/682 (Fall 2002) Ambient water quality standards Designated use: Describes the goal of the water quality standard –Examples: Swimming Boating Drinking water Wildlife Criterion: represents the condition of the waterbody that supports the designated use

Lecture ERS 482/682 (Fall 2002) Types of water quality criteria Pollutant load(s) from source(s) Ambient pollutant concentration in waterbody Human health and biological condition Controls on sources of pollution other than pollutants: –Land use –Characteristics of the channel/riparian zone –Flow regime –Species harvest condition NPDES permits (effluent stds) TMDL standard Instream flows; TMDL plans

Lecture ERS 482/682 (Fall 2002) Desirable criteria Measurable –Specify duration, frequency, and magnitude for chemical criteria Derived from the designated use –Biocriteria such as numeric measures of fish, benthic invertebrates, algae, etc.

Lecture ERS 482/682 (Fall 2002) Some problems with standards Standards that are not measurable –Problem: What do you do if you can’t measure as specified? Non-exceedence standard –Problem: Under what circumstances do you define exceedence? Flow restriction standards –Problem: Wet weather flows (storm runoff)

Lecture ERS 482/682 (Fall 2002) Integrity standards Integrity: biological condition of waterbodies that have not been altered by human activity BUT… No integrity does not necessarily mean the waterbody is impaired!!!

Lecture ERS 482/682 (Fall 2002) Biological integrity Figure 3: Karr and Chu (1999)

Lecture ERS 482/682 (Fall 2002) Integrity standards Indices (Box 3-5) –Index of Biological Integrity (IBI) Multimetric approach to assess biological condition Combines measures of condition in –Individuals –Populations –Assemblages –Landscapes Sites are scored according to metrics Overall score indicates the biological condition of the waterbody

Lecture ERS 482/682 (Fall 2002) Common pitfalls Expectation of simple correlations Inappropriate application of reference condition Inadequate sampling design Inappropriate consideration of sources of variability Incompatible data sets Inappropriate tests of metrics Etc. Karr and Chu (1999)

Lecture ERS 482/682 (Fall 2002) TMDL process Identify designated uses NRC (1999) Identify impaired water bodies Establish priority Allocate maximum total loadings of contaminants among sources

Lecture ERS 482/682 (Fall 2002) Allocation of maximum loads Determine relative contributions of different stressors Assess possible management options –Changes in hydrology –Changes in biology –Pollutant load limits MODELS CAN BE USEFUL HERE

Lecture ERS 482/682 (Fall 2002) Model selection Focus on standard/criteria Based on scientific theory Prediction uncertainty is reported Appropriately complex Appropriate for available data Credible to stakeholders Cost is feasible and sustainable Flexibility

Lecture ERS 482/682 (Fall 2002) TMDL process Identify designated uses NRC (1999) Identify impaired water bodies Establish priority Allocate maximum total loadings of contaminants among sources Implement controls Assess results Adaptive implementation

Lecture ERS 482/682 (Fall 2002) Figure 5-2: NRC (2001)

Lecture ERS 482/682 (Fall 2002) NRC (2001)