1. 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

2. Precipitations in Ohio Geographic Distribution (World Book)

3. Precipitations in Ohio Temporal Distribution (ODNR)

4. Streamflows in Ohio: Athens Gauging Station (USGS)

5. Streamflows in Ohio: Delaware Gauging Station (USGS)

6. As far as water is concerned, it is promised.
Ohio - Blessed Land
As far as
water is concerned,
it is promised.

7. Streamflows in Ohio: Athens Gauging Station (USGS)

8. 1988 Drought in the Midwest

9. 1988 Drought in the Midwest (Athens Messenger, 6-10-1988)

10. 1988 Drought in the Midwest (Athens Messenger, 6-9-1988)

11. 1988 Drought in the Midwest (Athens Messenger, 6-20-1988)

12. 1988 Drought in the Midwest (Athens Messenger, June 1988)

13. How to Define Droughts (AWRA Journal, October 1990)

14. A 100-year Drought? (AWRA Journal, October 1990)

15. Truncation Level of Drought Indicators Streamflow, Precipitation, Reservoir Level

16. Drought Definition Temperature and Groundwater Drawdown

17. Levels of Drought Severity

18. A Drought Monitoring Method
Operable under existing conditions
Palmer Drought Severity Index (Palmer, 1965)
Technically effective
Acceptable by all parties

19. Drought Indicators Streamflow Precipitation
Groundwater Level - drawdown
Temperature -
Reservoir Level -

20. Scioto River Basin

21. Streamflow Gauging Stations (18)

22. Example of Truncation Levels: Daily Streamflow
Olentangy River at Delaware
Mean daily flow: cms
70% Truncation Level: cms
80% Truncation Level: cms
90% Truncation Level: cms
95% Truncation Level: cms

23. Precipitation Gauging Stations (21)

24. Temperature Gauging Stations (13)

25. Groundwater Wells (14) & Reservoirs (4)

26. Precipitation Gauging Stations (21)

27. Mean Drought Durations

28. Conditional Probability from 70% to 80%

29. 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

30. Gauging Stations in the Basin

31. 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

32. Test for April 1988

33. Test for May 1988

34. Test for June 1988

35. 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?

36. Flood vs. Drought Reservoirs operated for flood control only
Can that be for drought management?

37. Four Reservoirs in the Basin

38. 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.

39. 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.

40. Expression of Area Factor

41. Expression of Distance Factor

42. Objective Function of the Optimization Model

43. Constraints for Minimum Flows at Control Stations

44. Constraints for Mass Conservation of Involved Reservoirs

45. Constraints for Minimum Releases from Involved Reservoirs

46. Example of Constraints for 70% Drought Severity

47. Example for Deer Creek- April 1988

48. Example for Deer Creek-May 1988

49. Example for Deer Creek-June 1988

50. Example for Paint Creek-May 1988

51. Example for Paint Creek-June 1988

52. Example for Paint Creek-July1988

53. Example Paint Creek-August 1988

54. Paint Creek - September 1988

55. Summary: The 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.

56. Yin: Shortage of water; Yang: Too much of water
Water in Ohio
Yin: Shortage of water; Yang: Too much of water
Yin and yang are complementary

57. Personal Reflections Equilibrium Water and Watershed
Conservation Mass, Energy, and Momentum
Equilibrium
Water and Watershed