OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Jason R. Vogel, Ph.D., P.E. Biosystems and Agricultural Engineering Oklahoma State University

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Where is the water?

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Where is the surface water in Oklahoma?

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 The Hydrologic Cycle  Precipitation – rain and snow  Runoff – over the land  Stream Flow –rivers and lakes (discharge)  Lake Storage  Infiltration – into the soil  Percolation – to ground water (recharge)  Evaporation and Evapotranspiration OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Source: Chow, Maidment, and Mays, Applied Hydrology, 1988

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 A Watershed is all the land that drains to one point on the landscape. If rain falls inside the watershed boundary, it flows toward the watershed outlet. P is precipitation

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 We measure rainfall in inches of depth. Depth x area = Volume 1 inch x 1 acre = 1 ac-inch or 27,000 gallons 1 foot x 1 acre = 1 ac-ft or 326,000 gallons Acres inches

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Precipitation in Oklahoma in inches 12.5 inches

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Evapotranspiration (ET) is evaporation plus transpiration ET is water that goes back to the atmosphere. Evapotranspiration

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Evapotranspiration – –Evaporation from rivers, lakes, bare soil, and vegetative surfaces –Evapotranspiration pumps water out of the ground through plant roots and leaves. The largest part of the hydrologic cycle (globally about 62% of rainfall returns directly to the atmosphere). OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Introduction to Hydrology Evaporation/Evapotranspiration

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Potential ET and Actual ET Lake Evaporation – close to Potential ET Potential ET (PET) – ET for a well-watered reference crop (turf grass or alfalfa) PET depends on the evaporative demand of the atmosphere air temperature, relative humidity, solar radiation, wind speed PET always exceeds Actual ET OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Introduction to Hydrology

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Actual ET Actual ET depends on how much water there is and what plants are involved. OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Introduction to Hydrology

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Annual Average PET

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Surface Water and Watersheds A Watershed is all the land that drains to one point on the landscape. OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Watershed Divide or Boundary Watershed Outlet

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Runoff and Stream Flow (Q) Runoff and Stream Flow Discharge, Q, is measured in cubic feet/second (cfs)

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Surface Water How do we describe surface water? –Lakes/Reservoirs: Stage (depth) Volume (ac-ft or gallons) –Rivers/Streams: Stage (depth) Discharge, Q (cfs) Velocity (ft/sec) OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Honey Creek near Grove, OK

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrograph – stream stage (ft) 11.0 ft of Stage 4.0 ft of Stage

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Hydrograph – Discharge (cfs) 10,000 cfs 1,000 cfs

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrograph and Rainfall 4 inch Rain

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Depends on soil texture - Conductivity Depends on vegetation and surface conditions –Soil Cover –Root density –Surface roughness Depends on soil wetness Depends on Compaction Infiltration is movement of water from surface into the soil

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Infiltration OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department –Soil Texture and Hydraulic Conductivity, K: Soil TextureTypical K (inches/hr) Sand4.64 Loamy Sand1.18 Loam0.13 Silt Loam0.26 Sandy Clay0.024 Clay0.012

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Estimating Runoff - What doesn’t infiltrate must runoff OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Q Infiltration capacity declines as soil gets wetter Infiltration capacity Rainfall Rate

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 –Amount of runoff depends on land cover Can be quantified through runoff coefficient… Runoff OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department DescriptionRunoff Coefficient Pavement: Asphalt, Concrete Lawns, sand soil: 2% (Flat) >7% (Steep) Residential: Single Family Apartments

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Hydrographs OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Source: Mays, Water Resources Engineering, 2001 Peak runoff rate Surface Runoffnoff

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Hydrographs OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Source: Mays, Water Resources Engineering, 2001 The water table supplies baseflow to the stream.

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrographs

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Shape of the hydrograph also depends on… OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Temporal distribution of rainfall Impervious areas of the watershed Ponds, diversions, and flood control structures Source: Mays, Water Resources Engineering, 2001

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Shape of the hydrograph depends on construction, compaction, and impervious area. OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Source: Mays, Water Resources Engineering, 2001 Before Impervious Area After construction

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Loads and Concentrations Concentration is measured as parts per million or mg/L. Load is the quantity of material per unit time – it is measured in Pounds/Day, Tons/Year, Kilograms/hour, grams/second. To measure load, you need both a concentration and flow rate: Load = Concentration x Discharge

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Hydrologists use Statistics… Hydrologic statistics  Frequency Analysis Magnitude of Storms, Floods, or even Drought can be described by its frequency. –Bigger events occur less frequently. –We can describe the size event by its expected frequency or Return Period. OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Return Period –Return Period (T) = average recurrence interval between events equaling or exceeding a specific magnitude OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Return Period – another way to look at it The probability of an event is the inverse of its return period. A10-yr storm has 1/10 or 10% chance of occurring in any given year. A 100-yr storm has 1% chance. Note: a 500-yr storm is bigger than a 100-yr storm, but it may not be much bigger. …and return period is estimated from the period of record – but we do not know the future.

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Hydrologic Considerations for Water Quality Everything in the watershed affects water quality, but not everything is equally effective. –Most pollutants travel with water – how much water determines when and how much the pollutants arrive. –Some water infiltrates the soil – and takes pollutants with it. –Some pollutants break down or become stabilized before they reach the water body. –Some pollutants originate near or in the stream (these are the first concern).

OKLAHOMA STATE UNIVERSITY Biosystems and Agricultural Engineering Department Hydrology 101 Hydrologic Considerations for Water Quality Nonpoint pollution is dependent on rainfall frequency (probability) –Does not occur every day –Magnitude of rainfall varies –Consider the return period or probability of occurrence Impervious areas transmit pollutants more effectively than areas where infiltration occurs. Roads make very efficient channels –carry water and pollutants.