Droughts in Ohio: Shall We be Worried?

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Droughts in Ohio Shall We be Worried?

• Tiao J. Chang
• Department of Civil Engineering
• Russ College of Engineering, Ohio University
• Athens, Ohio 45701
• Prepared for the WMAO 2009 Fall Conference
• November 5, 2009

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Precipitations in OhioGeographic Distribution
(World Book)

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Precipitations in OhioTemporal Distribution
(ODNR)
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Streamflows in OhioAthens Gauging Station
(USGS)
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Streamflows in OhioDelaware Gauging Station
(USGS)
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Ohio - Blessed Land

• As far as
• water is concerned,
• it is promised.

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Streamflows in OhioAthens Gauging Station
(USGS)
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1988 Drought in the Midwest
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1988 Drought in the Midwest (Athens Messenger,
6-10-1988)
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1988 Drought in the Midwest (Athens Messenger,
6-9-1988)
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1988 Drought in the Midwest (Athens Messenger,
6-20-1988)
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1988 Drought in the Midwest (Athens Messenger,
June 1988)
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How to Define Droughts(AWRA Journal, October
1990)
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A 100-year Drought?(AWRA Journal, October 1990)

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Truncation Level of Drought IndicatorsStreamflow
, Precipitation, Reservoir Level
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Drought DefinitionTemperature and Groundwater
Drawdown
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Levels of Drought Severity

• 70 Drought Severity
• 80 Drought Severity
• 90 Drought Severity
• 95 Drought Severity

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A Drought Monitoring Method

• Operable under existing conditions
• Palmer Drought Severity Index (Palmer, 1965)
• Technically effective
• Acceptable by all parties

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Drought Indicators

• Streamflow
• Precipitation
• Groundwater Level - drawdown
• Temperature -
• Reservoir Level -

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Scioto River Basin
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• Streamflow
• Gauging
• Stations (18)

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Example of Truncation Levels Daily Streamflow

• Olentangy River at Delaware
• Mean daily flow 10.00 cms
• 70 Truncation Level 0.911 cms
• 80 Truncation Level 0.651 cms
• 90 Truncation Level 0.453 cms
• 95 Truncation Level 0.312 cms

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• Precipitation
• Gauging
• Stations (21)

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• Temperature
• Gauging
• Stations (13)

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• Groundwater
• Wells (14)
• Reservoirs (4)

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• Precipitation
• Gauging
• Stations (21)

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Mean Drought Durations

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Conditional Probabilityfrom 70 to 80
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Severity Levels of Streamflow Drought

• Based on daily flow monitoring, a drought event
  is between two levels of severity
• Duration of current event Mean drought
  duration
• Conditional probability 0.50
• Levels of Severity Selection
• Gauging Stations
• Indicator majority of gauging stations

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Gauging Stations in the Basin
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Basinwide Drought Severity Levels

• Streamflow drought plus at least one other
  indicator exceeding the severity level of
  streamflow drought - Level of streamflow
  drought is selected.
• Streamflow drought plus at least one other
  indicator reaching 70 but not exceeding that of
  streamflow drought 70 is selected
• Streamflow not reaching 70 but at least two
  other indicators are 70 is selected

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Test for April 1988
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Test for May 1988
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Test for June 1988
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Summary The monitoring method

• Groundwater drawdown indicated the drought
  event at the earliest stage.
• Precipitation is the most sensitive drought
  indicator.
• Based on the definition as stated, streamflow
  becomes the most critical basinwide drought
  indicator?

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Flood vs. Drought

• Reservoirs operated for flood control only
• Can that be for drought management?

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Four Reservoirs in the Basin
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Requirements for the Optimization Model

• Minimum release is required for each reservoir.
• Minimum streamflow at control stations according
  to demands at a given drought severity level.
• Mass conservation of a reservoir.
• Minimum reservoir elevation for a reservoir.

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Assumptions for the Optimization Model

• Maximum Release - the amount enclosed between
  the specified reservoir elevation and the 70
  truncation level of the reservoir.
• Area Factor- contribution of a reservoir to a
  downstream control station is proportional to
  the drainage area of a reservoir.
• Distance Factor - contribution of a reservoir to
  a downstream control station is inversely
  proportional to the distance of the reservoir
  from the control station.

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Expression of Area Factor

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Expression of Distance Factor

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Objective Function of the Optimization Model

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Constraints for Minimum Flows at Control
Stations

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Constraints for Mass Conservation of Involved
Reservoirs

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Constraints for Minimum Releases from Involved
Reservoirs

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Example of Constraints for 70 Drought Severity

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Example for Deer Creek- April 1988

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Example for Deer Creek-May 1988

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Example for Deer Creek-June 1988

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Example for Paint Creek-May 1988

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Example for Paint Creek-June 1988

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Example for Paint Creek-July1988

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Example Paint Creek-August 1988

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Paint Creek - September 1988

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SummaryThe Optimization Method

• Daily monitoring of drought severity as defined
  enables an optimum model for management using
  flood-control reservoirs.
• The developed area factor and distance factor
  rationalize conflicting constraints for
  competing uses under the stress of water
  shortage.
• The safe yield of a reservoir estimated based on
  drought severity levels eases the operation of
  the reservoir.

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Water in Ohio

• Yin Shortage of water Yang Too much of water

Yin and yang are complementary
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Personal Reflections

• Conservation Mass, Energy, and Momentum
• Equilibrium
• Water and Watershed