Bays in Peril: A Natural Inflow Approach for Texas Estuaries Norman D. Johns, PhD, National Wildlife Federation Warren Pulich, PhD, Texas State University

The Natural Flow Paradigm “managing an ecosystem within its range of natural variability is an appropriate path to maintaining diverse, resilient, productive, and healthy systems” (Swanson et al. 1993) general Maintain “full natural range of variation of hydrologic regimes...” measured by – timing, frequency, duration, and rate of change of key biologically significant hydro events (Richter et al. 1997) flows

3 step

Corpus Christi Caller-Times, Sept. 24, 2003

3 step

High Variability is Inherent Galveston Bay Measured Freshwater Inflows High Variability is Inherent

Shrimp & Freshwater Inflows

NWF’s Ecologically Relevant Inflow Criteria productivity maintenance- 4 month spring/early summer freshwater inflow pulse (a.k.a. “Freshete”) 1.

Oysters & Freshwater Inflows

NWF’s Ecologically Relevant Inflow Criteria productivity maintenance- 4 month spring/early summer freshwater inflow pulse (a.k.a. “Freshete”) 1. drought analysis – 6 consecutive months very low-inflows, between Mar. – Oct. 2.

WAM = Hydrology Tool - predict inflows - differing scenarios: Natural Conditions Current Use Full Water Rights Levels of reuse - monthly results

Assessing Springtime Freshwater Pulse

Degree of Alteration = 60%

National Wildlife Federation Analysis of Estuary Inflows productivity maintenance- spring Freshete drought analysis - population survival

NWF’s Low Flow Assessment [ MinQsal ]

Degree of Alteration > 500%(high)

Next Steps Application to Regional Planning Process Refinement of Criteria (time window, benchmark volumes based on natural stats.) Further examine ecological relevance of criteria