Hydrologic Overview & Quantities It is important to understand the big picture when attempting to forecast. This includes the interactive components and hydrologic quantities.

Hydrologic Cycle

The complexity of what we are trying to accomplish…. Infiltration Evaporation & Condensation The Water Budget Photosynthesis & Respiration Antecedent Moisture Conditions Transpiration & Interception Variable Source Area Time of Concentration The “sphere” concept was borrowed from Dr. Peter Black: Watershed Hydrology – 2 nd Edition, Peter Black, 1996, Ann Arbor Press (ISBN# )

Models try to mimic this! Basin Process Representation Infiltration Excess Precip. Interception Storage Time Series

From A Basin View Excess Precip. Model Excess Precip. Basin “Routing” Runoff Hydrograph Stream “Routing”

The Runoff Picture Hydrology is long term and short term…. Hydrology is long term and short term…. In this course we will mainly focus on the short term: In this course we will mainly focus on the short term: Floods & flood flows. Floods & flood flows. Generating runoff/high flows. Generating runoff/high flows. Predicting/forecasting flows. Predicting/forecasting flows. Space/time scales. Space/time scales.

Recipe(s) for a Flood/High Flows What causes a flood / high flow? What causes a flood / high flow? What are the conditions? What are the conditions? What are the types of flooding situations? What are the types of flooding situations? Your area or other areas….. Your area or other areas…..

What Are the Defining Characteristics of a Flood? Timing – rise time, recession, duration. Timing – rise time, recession, duration. Flows – peak flows, magnitude (statistical). Flows – peak flows, magnitude (statistical). Precipitation – intensity, duration, frequency…. Precipitation – intensity, duration, frequency….

What Controls the Timing, Flow, and Precipitation? The hydrology – short term and long term. The hydrology – short term and long term. The meteorology – short term (weather/storm type) and long term (climate). The meteorology – short term (weather/storm type) and long term (climate).

Short Term Weather (storm type) & “current hydrologic conditions”

Watershed Characteristics Area Area Slope Slope Land Use Land Use Soils Soils Geology Geology Climate Climate Geomorphology Geomorphology

Some of the “Right” Combinations…. Precipitation –vs.- infiltration Precipitation –vs.- infiltration –Precipitation intensity > infiltration rate –Precipitation total > infiltration capacity –“Storage” in the system is full –Human induced high water or flows –Natural alterations to the watershed

Our Focus - Forecasting Must be both short & long term.. Must be both short & long term.. The combination(s) of precipitation and hydrologic conditions that lead create a potential flooding situation… The combination(s) of precipitation and hydrologic conditions that lead create a potential flooding situation… “basin hydrology” – basin hydrology looks at the hydrologic budget in both the short and long term. “basin hydrology” – basin hydrology looks at the hydrologic budget in both the short and long term.

How much water is there? Distribution of Earth's Waters and Residence Times....

Units & Properties of Water

Area 1 acre = 43,560 ft 2 1 acre = 43,560 ft 2 1 mi 2 = 640 acres 1 mi 2 = 640 acres 1 hectare = 100m x 100m = acres = 10,000 m 2 1 hectare = 100m x 100m = acres = 10,000 m 2 1 km 2 = mi 2 1 km 2 = mi 2 Some Common Unit Conversions

Volume 1 acre-foot = 1 ac-ft = 1 acre of water x 1 foot deep = 43,560 x 1 = 43,560 ft 3 1 acre-foot = 1 ac-ft = 1 acre of water x 1 foot deep = 43,560 x 1 = 43,560 ft 3 1 ac-inch = 1 acre x 1 inch deep = 43,560 x 1/12 = 3,630 ft 3 1 ac-inch = 1 acre x 1 inch deep = 43,560 x 1/12 = 3,630 ft 3 1 ft 3 = 7.48 gallons 1 ft 3 = 7.48 gallons 1 gallon H 2 O ~ 8.34 lbs. 1 gallon H 2 O ~ 8.34 lbs.

Runoff Volume 1-inch of runoff over 1 square mile :1-inch of runoff over 1 square mile : 1/12 feet x 1 mi 2 x 640 acres/mi 2 x 43,560 ft2/mi 2 = 2,323,200 ft 3 1/12 feet x 1 mi 2 x 640 acres/mi 2 x 43,560 ft2/mi 2 = 2,323,200 ft 3

Discharge 1 cfs = 1 cubic foot per second 1 cfs = 1 cubic foot per second 1 cfs x 7.48 gal/ft 3 x 3600 sec/hr x 24 hrs/day = 646,272 gpd = MGD 1 cfs x 7.48 gal/ft 3 x 3600 sec/hr x 24 hrs/day = 646,272 gpd = MGD 1 cfs x 3600 sec/hr x 24 hrs/day = 86,400 cfs/day 1 cfs x 3600 sec/hr x 24 hrs/day = 86,400 cfs/day 86,400 cfs/day x 1 ac-ft/43,560 ft 3 = ac-ft/day (~ 2 ac-ft/day) 86,400 cfs/day x 1 ac-ft/43,560 ft 3 = ac-ft/day (~ 2 ac-ft/day) ac-ft/day x 12 inches/ft x 1 day/24 hrs = ac-in/hr ac-ft/day x 12 inches/ft x 1 day/24 hrs = ac-in/hr 1 ac-in/hr x 43,560 ft 3 /ac-ft x 1 hr/3600 sec x 1 ft/12 inches = cfs 1 ac-in/hr x 43,560 ft 3 /ac-ft x 1 hr/3600 sec x 1 ft/12 inches = cfs

Power Hp =  HQ/550 Hp =  HQ/550 1 hp = 550 ft*lb/sec = kilowatts 1 hp = 550 ft*lb/sec = kilowatts  weight of water H = head or elevation difference Q = flow Hydropower wants a lot of flow and a full reservoir…..