The State Methodology for determination of freshwater inflow needs of the Texas bays

The State Methodology for determination of freshwater inflow needs of the Texas bays Overview & Critique Presentation to: Science Advisory Committee Study Commission on Water for Environmental Flows 18 June 2004 George H. Ward Center for Research in Water Resources University of Texas at Austin

Sabine Lake Galveston Bay Matagorda Bay San Antonio Bay Aransas-Copano Bays Corpus Christi Bay Upper Laguna Madre- Baffin Bay Lower Laguna Madre

ESTUARY coastal waterbody semi-enclosed free connection to open sea influx of sea water freshwater influx small to intermediate scale

transitional systems, between freshwater and marine ESTUARIES transitional systems, between freshwater and marine transitional systems, between freshwater and marine hydrography and chemical qualities governed by both terrestrial and marine controls, as well as factors unique to estuary hydrography and chemical qualities governed by both terrestrial and marine controls, as well as factors unique to estuary terrestrial controls: freshwater influxes, flooding and inundation, runoff and inflow loads (sediment, nutrients, pollutants), and atmospheric deposition terrestrial controls: freshwater influxes, flooding and inundation, runoff and inflow loads (sediment, nutrients, pollutants), and atmospheric deposition marine controls: tides, waves, non-astronomical sea-level variations, marine storms, salinity, and littoral sediment influx marine controls: tides, waves, non-astronomical sea-level variations, marine storms, salinity, and littoral sediment influx predominance of these factors depends upon position in estuary: pronounced environmental gradients predominance of these factors depends upon position in estuary: pronounced environmental gradients extreme time variability in estuary extreme time variability in estuary

cross section view (longitudinal-vertical) plan view (surface horizontal)

ESTUARIES wide range in habitats spanning the estuarine zone majority of the larger animals in estuary only temporarily for specific biological purposes

ESTUARIES wide range in habitats spanning the estuarine zone majority of the larger animals in estuary only temporarily for specific biological purposes complex and shifting food webs, with frequent overlap between planktonic, pelagic and benthal communities substantial time variations in all of above factors, resulting in marked variability in community make-up and abundance abundance of specific organism depends on: population capable of entering system (i.e., abundance/health of source population, and capability to negotiate entrance into the system) availability of suitable physico-chemical conditions and/or food sources

This sequence of slides is an attempt to capsulize the entire estuarine ecosystem. This first slide displays the major biological communities, with flora as the base of the ecosystem, and the consumer communities somewhat eccentrically subdivided into those that are eaten by humans ("seafood organisms") and those that are not ("non-fishery consumer"). In the estuary, immigration from the sea, "recruitment", is a major determinant of the communities within the bay, but, of course, shrimp people are very familiar with this.

This couples the chemical environment with the biological This couples the chemical environment with the biological. Light and nutrients are of course the primary controls on flora, light being modulated by suspended matter, of particular potential importance in our project area because of the large sediment loads. Among the "other constituents", most important is dissolved oxygen, which is given more attention later. It's noteworthy at this point that the diagram applies as well to a shrimp pond, if "recruitment" is generalized to include stocking, and "other constituents" includes feeding.

The major complexity of the estuarine ecosystem is the processes that control the concentrations and distribution of chemical parameters within the system, shown here. While no one really cares about estuary circulation (a.k.a. hydrodynamics) as a management endpoint, it must be addressed to understand the distribution of waterborne parameters, which usually are the management endpoint. Note that any one of these major boxes could be considerably expanded.

Potential freshwater inflow effects on estuary  dilutes seawater  carries nutrients, trace constituents, and terrestrial sediments into estuary  contributes to gradient of water properties across estuary  produces inundation and flushing of important zones, due to short-term flooding  variability over time creates fluctuation in estuarine properties, important to ecosystem function  source of renewal water

STATE METHODOLOGY FOR DETERMINING INFLOW REQUIREMENTS OF THE TEXAS BAYS An overview & summary

San Antonio Bay

OPTIMAL INFLOWS FOR SAN ANTONIO BAY

OPTIMAL INFLOWS FOR GALVESTON BAY

Max H Specification Objective goal: Maximal harvest Species weights: equal Min Q Specification Objective goal: Minimal total annual inflows

Max H Specification Objective goal: Maximal harvest Species weights: equal Constraints: Monthly inflow: >lower decile (10th percentile) <historical monthly median Bimonthly inflows:>specified values (>sum of lower decile values) Salinity: bounded by “consensus” viability limits Min Q Specification Objective goal: Minimal total annual inflows Harvest: >80% of historical mean for each species

FUNDAMENTAL ASSUMPTIONS OF THE STATE METHODOLOGY ECOLOGICAL HEALTH IS MEASURED BY THE ABUNDANCE OF 6-10 KEY SPECIES

For San Antonio Bay, the 7 key species are: blue crab brown shrimp oyster white shrimp red drum black drum spotted seatrout

For Galveston Bay, the 8 key species are: blue crab brown shrimp oyster white shrimp red drum black drum spotted seatrout flounder

For Sabine Lake, the 8 key species are: blue crab brown shrimp menhaden white shrimp red drum croaker spot speckled trout

FUNDAMENTAL ASSUMPTIONS OF THE STATE METHODOLOGY ECOLOGICAL HEALTH IS MEASURED BY THE ABUNDANCE OF 6-10 KEY SPECIES ABUNDANCE IS PROPORTIONAL TO, HENCE MEASURED BY, THE ANNUAL COMMERCIAL HARVEST

Advantages of harvest as a measure of abundance:  the data are quantitative and consistently measured  the data represent the catch integrated over large aquatic areas, so the effect of spatial variability should be averaged out  a long period of record of annual harvests is available extending back in some cases five decades  the harvest measures one of the direct economic benefits of the resource of an estuary

Disadvantage of harvest as a measure of abundance: Harvest is affected by factors having no relation to abundance:  regulation of the fishery  location, catch and processing technology of the fleet  skill of the fisherman  market and economics  external stresses on the species population

FUNDAMENTAL ASSUMPTIONS OF THE STATE METHODOLOGY ECOLOGICAL HEALTH IS MEASURED BY THE ABUNDANCE OF 6-10 KEY SPECIES ABUNDANCE IS PROPORTIONAL TO, HENCE MEASURED BY, THE ANNUAL COMMERCIAL HARVEST ABUNDANCE IS QUANTIFIED ENTIRELY BY 6 BIMONTHLY FLOWS, TOTALLED OVER THE ENTIRE BAY

6 independent flow variables ( “seasonal” flows): Jan + Feb Mar + Apr May + Jun Jul + Aug Sep + Oct Nov + Dec each computed by: Inflow = Gauged + Ungauged - Diversions + Returns (summed over the entire bay)

FUNDAMENTAL ASSUMPTIONS OF THE STATE METHODOLOGY ECOLOGICAL HEALTH IS MEASURED BY THE ABUNDANCE OF 6-10 KEY SPECIES ABUNDANCE IS PROPORTIONAL TO, HENCE MEASURED BY, THE ANNUAL COMMERCIAL HARVEST ABUNDANCE IS QUANTIFIED ENTIRELY BY 6 BIMONTHLY FLOWS, TOTALLED OVER THE ENTIRE BAY ABUNDANCE VARIES IN PROPORTION TO THE BIMONTHLY BAY-TOTAL FLOWS (perhaps log transformed)

 the relationship can be extracted by linear regression  harvest is completely determined by the levels of inflow for a given year (apart from perhaps lagging harvest behind inflow based upon the grow-out time of the species): there is no memory  there is no substantial effect of recruitment or dynamics of the Gulf stock  recreational harvest is irrelevant

HARVEST REGRESSIONS FOR SAN ANTONIO BAY H = annual commercial landings, thousands of pounds Qab = total bimonthly inflow, ac-ft, for sequential months a and b Crab: H = 110.64 – 145.3 ln(QJF) + 332.5 ln (QJA) – 141.4 ln(QSO)   Oyster: H = 3000.7 + 180.4 ln(QMA) – 963.3 ln(QMJ) + 710.0 ln(QJA) – 231.5 ln(QSO)    R.drum: H = 32.786 + 0.0797 QMJ + 0.2750 QJA - 0.2010 QND B.drum: H = -18.087 + 0.2411 QJF - 0.1734 QMA + 0.0850 QND Trout: ln(H) = 2.6915 – 0.7185 ln(QMA) + 1.860 ln(QMJ) – 1.086 *ln(QND) B. shr: ln(H)= 6.5679 + 0.6707 ln(QJA) – 0.7486 ln(QSO) W. shr: H = 545.59 + 160.9 ln(QJF) + 279.1 ln(QMJ) – 155.1 ln(QJA) – 277.9 *ln(QND)

HARVEST REGRESSIONS FOR GALVESTON BAY H = annual commercial landings, thousands of pounds Qab = total bimonthly inflow, ac-ft, for sequential months a and b   Crab: H = 751.23 - 0.2756 QJF + 0.8464 QMA - 0.139 QMJ - 0.4747 QSO + 0.6001 QND Oyster: H = 4169.8 - 0.9397 QJF +0.2838 QMJ - 0.9445 QJA Brown shrimp: H = 1019.8 - 0.5779 QJF + 0.4192 QJA + 0.4060 QSO + 0.3533 QND White shrimp: H = 3212 - 0.6905 QJF + 0.2734 QMA - 0.3254 QJA + 0.5046 QND Flounder: H = -12.122 - 0.0309 QJF + 0.0541 QJA + 0.0494 QND Red drum: ln H = 3.1548 + 3.92E-4 QMJ - 2.04E-3 QJA + 6.98E-4 QSO Black drum: H = 50.225 - 0.02985 QJF + 0.1040 QJA - 0.0639 QSO + 0.0329 QND Seatrout: ln H = 8.2764 - 1.8241 ln QJF +1.425 ln QND

FUNDAMENTAL ASSUMPTIONS OF THE STATE METHODOLOGY ECOLOGICAL HEALTH IS MEASURED BY THE ABUNDANCE OF 6-10 KEY SPECIES ABUNDANCE IS PROPORTIONAL TO, HENCE MEASURED BY, THE ANNUAL COMMERCIAL HARVEST ABUNDANCE IS QUANTIFIED ENTIRELY BY 6 BIMONTHLY FLOWS, TOTALLED OVER THE ENTIRE BAY ABUNDANCE VARIES IN PROPORTION TO THE BIMONTHLY BAY-TOTAL FLOWS (perhaps log transformed) OPTIMUM FLOWS ARE NECESSARY FOR MAINTENANCE OF ECOLOGICAL HEALTH

TxEMP MinQ and MaxH Solutions

OPTIMAL INFLOWS FOR GALVESTON BAY

Mid-Galveston Bay salinity versus Trinity River flow

LOWER NUECES BAY

SN = salinity in ppt for month N Regressions of salinity versus monthly inflows for Galveston Bay regions SN = salinity in ppt for month N QM = monthly combined inflow in ac-ft for month M Trinity Bay SN = 49.109 - 3.221 * log(QN-1) - 3.039 * log(QN-2) Red Bluff SN = 42.438 - 3.567 * log(QN-1) - 1.179 * log(QN-2) Dollar Point SN = 48.803 - 4.316 * log(QN-1) - 0.757 * log(QN-2)

SALINITY VIABILITY LIMITS (ppt) FOR GALVESTON BAY

Sabine Lake

HERE BEGINS CRITICISM

Disaggregated relative contributions of species and bimonthly flow to total computed harvest Galveston Bay MaxH flows const QJF QMA QMJ QJA QSO QND ratio to total harvest Flow (MaxH) 0.0586 0.2464 0.4052 0.0674 0.0348 0.1876   Blue crab 0.0643 -0.0072 0.0932 -0.0333 -0.0074 0.0503 0.160 Oyster 0.3571 -0.0246 0.0514 -0.0284 0.355 Red drum 0.0020 0.0018 -0.0016 0.0003 0.003 Black drum 0.0043 -0.0008 0.0031 -0.0010 0.0028 0.008 Spotted seatrout 0.029 Brown shrimp 0.0873 -0.0151 0.0126 0.0063 0.0296 0.121 White shrimp 0.2751 -0.0181 0.0301 -0.0098 0.0423 0.320 Flounder -0.0010 -0.0008 0.0016 0.0041 0.004  TOTAL 0.7891 -0.0666 0.1233 0.0199 -0.0224 -0.0018 0.1290 1.000

Galveston Bay

Galveston Bay

San Antonio Bay oyster harvest

Brown shrimp regression equations variables: const JF MA MJ JA SO ND Brown shrimp regression equations Galveston Bay H = 1020 -0.58 QJF + 0.42 QJA + 0.41 QSO +0.35 QND San Antonio Bay log H = 6.57 + 0.67 log QJA -0.75 log QSO Corpus Christi Bay log H = 7.94 +0.30 log QMA -0.52 log QSO Black drum regression equations Galveston Bay H = 50.22 -0.03 log QJF +0.10 log QJA -0.06 log QSO +0.03 log QND San Antonio Bay H = -18.09 +0.24 QJF -0.17 QMA +0.09 QND Corpus Christi Bay H = -47.74 +44.5 +25.6 log QJA +15.6 log QND

Statistical data for Corpus Christi Bay regressions Species Data points R2 S.E used deleted Black drum 31 2 0.79 57 Flounder 23 10 0.52 0.62 Blue crab 27 6 0.37 0.97 Red drum 20 0 0.85 0.58 Spotted seatrout 20 0 0.93 0.29 Brown shrimp 22 14 0.62 0.26 White shrimp 16 20 0.64 0.26

HOW WELL DOES A BAY-TOTAL INFLOW DEPICT THE BIOLOGICAL RESPONSE?

HOW ACCURATELY DO TWO-MONTH BINS DEPICT THE TIME-VARIATION OF INFLOW TO A TEXAS BAY?

Spring freshet on the Guadalupe at Victoria

Fall freshet on the Trinity at Romayor

HOW SENSITIVE IS THE OPTIMIZATION SOLUTION, ANYWAY?

Max H Specification Objective goal: Maximal harvest Species weights: equal Constraints: Monthly inflow: >lower decile (10th percentile) <historical monthly median Bimonthly inflows:>specified values (>sum of lower decile values) Salinity: bounded by “consensus” viability limits Min Q Specification Objective goal: Minimal total annual inflows Harvest: >80% of historical mean for each species

DOES NATURE EXHIBIT AN OPTIMUM CONSISTENT WITH THE MODEL PREDICTION?

1.79 0.45 0.47 0.53 0.45

.27 .07 .05 .02 .03 .05 .05

Galveston Bay

San Antonio Bay

DOES AN OPTIMAL INFLOW OCCUR IN NATURE?

San Antonio Bay monthly flows within 10% of maxH

San Antonio Bay monthly flows within 10% of maxH (continued)

San Antonio Bay monthly flows within 20% of maxH

San Antonio Bay monthly flows within 20% of maxH

FUNDAMENTAL ASSUMPTIONS OF THE STATE METHODOLOGY ECOLOGICAL HEALTH IS MEASURED BY THE ABUNDANCE OF 6-10 KEY SPECIES ABUNDANCE IS PROPORTIONAL TO, HENCE MEASURED BY, THE ANNUAL COMMERCIAL HARVEST ABUNDANCE IS QUANTIFIED ENTIRELY BY 6 BIMONTHLY FLOWS, TOTALLED OVER THE ENTIRE BAY ABUNDANCE VARIES IN PROPORTION TO THE BIMONTHLY BAY-TOTAL FLOWS (perhaps log transformed) sufficient OPTIMUM FLOWS ARE NECESSARY FOR MAINTENANCE OF ECOLOGICAL HEALTH

CONCLUDING CONCERNS

Should more species, or other ecological variables, be addressed? Should other factors, in addition to inflows, be considered in the prediction problem? Are the analytical methods sufficiently sophisticated for the complexity of the problem?

Is this an optimization problem Is this an optimization problem? Are optimal average conditions even relevant? Is it necessary to take account of year-to-year variation in estuary conditions? I.e., does a Texas bay have “memory”?