the state methodology for determination of freshwater inflow needs of the texas bays

The State Methodologyfor determination of freshwater inflow

needs of the Texas bays

The State Methodologyfor determination of freshwater inflow

needs of the Texas bays

George H. WardCenter for Research in Water Resources

University of Texas at Austin

Overview & Critique

Presentation to:

Science Advisory Committee

Study Commission on Water for Environmental Flows

18 June 2004

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

ESTUARIEStransitional systems, between freshwater and marine

hydrography and chemical qualities governed by both terrestrial and marine controls, as well as factors unique to estuary

predominance of these factors depends upon position in estuary: pronounced environmental gradients

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

transitional systems, between freshwater and marine

hydrography and chemical qualities governed by both terrestrial and marine controls, as well as factors unique to estuary

predominance of these factors depends upon position in estuary: pronounced environmental gradients

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

extreme time variability in estuaryextreme time variability in estuary

cross section view(longitudinal-vertical)

plan view(surface horizontal)

ESTUARIESwide range in habitats spanning the estuarine zone

majority of the larger animals in estuary only temporarily for specific biological purposes

ESTUARIESwide range in habitats spanning the estuarine zone

majority of the larger animals in estuary only temporarily for specific biological purposes

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

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

Potential freshwater inflow effects on estuary

source of renewal water

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

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 SpecificationObjective goal: Maximal harvest

Species weights: equal

Min Q Specification

Objective goal: Minimal total annual inflowsSpecies weights: equal



Constraints:Monthly inflow: >lower decile (10th percentile)

<historical monthly medianBimonthly inflows:>specified values (>sum of lower decile values)Salinity: bounded by “consensus” viability limits

Min Q Specification

Objective goal: Minimal total annual inflowsSpecies weights: equalConstraints:Harvest: >80% of historical mean for each speciesMonthly inflow: >lower decile (10th percentile)


FUNDAMENTAL ASSUMPTIONSOF THE STATE METHODOLOGY

ECOLOGICAL HEALTH IS MEASURED BY THE ABUNDANCE OF 6-10 KEY SPECIES

blue crab brown shrimp

oyster white shrimp

red drum black drum

spotted seatrout

For San Antonio Bay, the 7 key species are:


oyster white shrimp

red drum black drum

spotted seatrout flounder

For Galveston Bay, the 8 key species are:


menhaden white shrimp

red drum croaker

spot speckled trout

For Sabine Lake, the 8 key species are:



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




ABUNDANCE IS QUANTIFIED ENTIRELY BY 6 BIMONTHLY FLOWS, TOTALLED OVER THE ENTIRE BAY

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)

6 independent flow variables ( “seasonal” flows):





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 BAYH = annual commercial landings, thousands of poundsQab = 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)

H = annual commercial landings, thousands of poundsQab = 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

Brownshrimp: H = 1019.8 - 0.5779 QJF + 0.4192 QJA + 0.4060 QSO + 0.3533 QND

Whiteshrimp: 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

Blackdrum: 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

HARVEST REGRESSIONS FOR GALVESTON BAY





OPTIMUM FLOWS ARE NECESSARY FOR MAINTENANCE OF ECOLOGICAL HEALTH

ABUNDANCE VARIES IN PROPORTION TO THE BIMONTHLY BAY-TOTAL FLOWS (perhaps log transformed)

TxEMP MinQ and MaxH Solutions

OPTIMAL INFLOWS FOR GALVESTON BAY

Mid-Galveston Bay salinity versus Trinity River flow

LOWER NUECES BAY

Regressions of salinity versus monthly inflows for Galveston Bay regions

SN = salinity in ppt for month NQM = 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 tototalharvest

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 0.160Oyster 0.3571 -0.0246 0.0514 -0.0284 0.355Red drum 0.0020 0.0018 -0.0016 0.0003 0.003Black drum 0.0043 -0.0008 0.0031 -0.0010 0.0028 0.008Spotted seatrout 0.029Brown shrimp 0.0873 -0.0151 0.0126 0.0063 0.0296 0.121White shrimp 0.2751 -0.0181 0.0301 -0.0098 0.0423 0.320Flounder -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

San Antonio Bay oyster harvest

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

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 QJF

Brown shrimp regression equations

Black drum regression equations

variables: const JF MA MJ JA SO ND

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

Species Data points R2 S.E

used deleted

Statistical data for Corpus Christi Bay regressions

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?



Constraints:Monthly inflow: >lower decile (10th percentile)


Min Q Specification

Objective goal: Minimal total annual inflowsSpecies weights: equalConstraints:Harvest: >80% of historical mean for each speciesMonthly inflow: >lower decile (10th percentile)


DOES NATURE EXHIBIT AN OPTIMUM CONSISTENT WITH THE MODEL

PREDICTION?

0.45 0.450.47 0.531.79

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

Galveston Bay

San Antonio Bay

DOES AN OPTIMAL INFLOWOCCUR IN NATURE?

MaxH 111.2 124.2 52.42 52.42 222.6 162.7 88.61 88.33 52.42 52.42 73.83 66.2 within 10% Month year J F M A M J J A S O N D

1941 1942 1943 170.4 1944 121.1 92.0 1945 52.2 1946 1947 89.0 69.2 1948 52.5 1949 221.2 50.3 72.6 1950 1951 1952 53.2 1953 50.8 1954 1955 1956 1957 1958 1959 109.7 1960 114.3 1961 1962 159.0 1963 53.3 1964 52.1 90.0 1965 53.8 1966 74.6 65.0 1967 1968 1969 166.9 1970

San Antonio Bay monthly flows within 10% of maxH

MaxH 111.2 124.2 52.42 52.42 222.6 162.7 88.61 88.33 52.42 52.42 73.83 66.2 Month year J F M A M J J A S O N D

1971 1972 1973 1974 1975 1976 111.0 1977 1978 167.0 1979 1980 76.0 1981 1982 111.2 1983 1984 1985 1986 124.2 1987 1988 53.6 1989 1990 1991 214.4 164.4 1992 1993 1994 1995 1996 1997 1998 1999 121.8

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


1941 1942 135.4 1943 170.4 56.7 79.0 1944 121.1 92.0 1945 150.1 52.2 1946 103.3 1947 89.0 55.9 80.3 69.2 1948 52.5 49.5 1949 221.2 50.3 72.6 1950 56.3 1951 1952 203.9 53.2 1953 119.2 50.8 70.5 1954 55.3 1955 1956 1957 1958 1959 109.7 1960 114.3 1961 1962 159.0 1963 53.3 56.6 1964 52.1 90.0 1965 83.5 53.8 1966 74.6 65.0 1967 1968 1969 166.9 1970



1971 48.0 1972 1973 134.3 202.2 1974 153.0 1975 1976 111.0 1977 95.9 1978 114.2 167.0 1979 80.8 1980 76.0 1981 1982 111.2 70.7 1983 1984 1985 116.3 1986 124.2 1987 240.2 1988 53.6 1989 1990 47.2 1991 214.4 164.4 1992 1993 1994 1995 82.1 66.5 1996 1997 1998 122.3 1999 121.8






OPTIMUM FLOWS ARE NECESSARY FOR MAINTENANCE OF ECOLOGICAL HEALTH

ABUNDANCE VARIES IN PROPORTION TO THE BIMONTHLY BAY-TOTAL FLOWS (perhaps log transformed) sufficient

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? 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”?

the state methodology for determination of freshwater inflow needs of the texas bays

Documents

freshwater influxes

marine storms

estuary predominance

marine hydrography

inflow requirements

factors unique

gradient of water properties

marked variability