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Chapter 3 -Hydrology Hwk#3 - pp. 85-87 2,4,7,11 Hydrologic Cycle Runoff - Ground Surface Water

Chapter 3 -Hydrology Hwk#3 - pp. 85-87 2,4,7,11 Hydrologic Cycle Runoff - Ground Surface Water Infiltration - Ground Penetration (percolation) Transpiration - Water goes through vegetation and then is released into the air as vapor

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Chapter 3 -Hydrology Hwk#3 - pp. 85-87 2,4,7,11 Hydrologic Cycle Runoff - Ground Surface Water

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  1. Chapter 3 -Hydrology • Hwk#3 - pp. 85-87 2,4,7,11 • Hydrologic Cycle • Runoff - Ground Surface Water • Infiltration - Ground Penetration (percolation) • Transpiration - Water goes through vegetation and then is released into the air as vapor • Evapotranspiration - Is the combination of evaporation and transpiration (>50% of precipitation)

  2. Chapter 3 -Hydrology 1. Rainfall Volume - acre-ft., hectares(ha) (V=Area x depth) Rainfall intensity - rate at which rain falls (in/hr. , mm/hr.) Recurrence Interval (N) years - the average time span between identical storms over a long period of time (i.e. 5 year storm- same as return period) Probability of occurence (1/N) - is the statistic of occurence in a single year

  3. Chapter 3 -Hydrology • 2. Surface Water • A. Water Sheds • Drainage Basin - Land which contributes runoff • to a river or stream • Confluence - the point at which two streams converge • Tributary - streams that feed into a first-order stream Subbasin Tributary Drainage Basin Outlet

  4. Chapter 3 -Hydrology • 2. Surface Water • B. Streamflow • Discharge - Volume per unit time • Hydrograph - flow response of a stream for a particular rainfall event (fig.3.15) • Perennial - streams that have a base flow from ground water • Intermittent or Ephemeral Stream-Streams that dry up after the rainfalls • Stage - the water surface above a referenced level • Weir - used to measure volume flow rate • Droughts - a long period of dry weather • MA7CD10 Flow - Minimum Average 7 Consecutive Day 10 - year flow - 90% chance that the minimum weekly discharge will be greater than the MA7CD10. Design parameter for water pollution control projects.

  5. Chapter 3 -Hydrology 3. Reservoirs • Summation Hydrograph - Determines when the reservoir is filling up or what is the minimum required storage volume. (fig. 3.20) • Uniform Withdrawal or Yield Line - Is the amount of water the reservoir can supply in a specific time period without going dry. (Predetermined by the demand on the reservoir) • Minimum Storage Volume Req’d - The minimum volume of water required in the reservoir in order to prevent a drought from depleting it. • Sediments behind a Dam - Causes a problem for vegetation and wildlife who rely on warmer temperatures and nutrients from silts and other deposited materials.

  6. Chapter 3 -Hydrology 4. Aquifers & Well Points • Aquifers - Is an underground stream.(fig 3.26) • Well Points - Perforated pipes that penetrate underground acquifers or water table • Darcy Law - V= K X S • where K - permeability coeff., mm/s • V - Flow velocity, mm/s • S - slope of the water table • Drawdown - The elevation distance between the pumping level and the static level.(fig. 3.28)

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