131.%20Surface%20Water

131.%20Surface%20Water - Surface Water Lecture 13...

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Unformatted text preview: Surface Water Lecture 13 Hydrologic Cycle Precipitation Runoff + Runoff Infiltration + Infiltration Evaporation + Evaporation Transpiration + Transpiration Storage Storage Lecture 13: Surface Water Page 1 of 18 Lecture 13: Surface Water Terms of the Water Cycle Precipitation Integration of point data Integration Depends upon storm type Depends Depends upon duration Depends Statistical techniques Statistical Obtain average value Obtain Lecture 13: Surface Water Page 2 of 18 Lecture 13: Surface Water Storm Characteristics Thunderstorm rainfall map Regional storm rainfall map Recurrence Interval Lecture 13: Surface Water Page 3 of 18 Lecture 13: Surface Water Record Rains Texas Coast Record Rains Texas Coast Lecture 13: Surface Water Page 4 of 18 Lecture 13: Surface Water Record Rains Texas Coast 2002 Hill Country Storm Lecture 13: Surface Water Page 5 of 18 Lecture 13: Surface Water Runoff Determine stream Determine stage-time Use Q = Av to Use calibrate Determine total Determine runoff Assumes NO Assumes sediment transport or erosion Open Channel Flow Q = Av Q = Discharge (volume/time) A = Cross Sectional Area v = Average Flow Velocity Lecture 13: Surface Water Page 6 of 18 Lecture 13: Surface Water Non-Uniform Channel Flow Manning’s Equation V = (1.49/n)R2/3S1/2 V = Average Velocity R = Hydraulic Radius S = Slope n = Manning’s Number Lecture 13: Surface Water Page 7 of 18 Lecture 13: Surface Water Manning’s Number n Channel Characteristics Channel Flow Lecture 13: Surface Water Page 8 of 18 Lecture 13: Surface Water Infiltration Initially very high Initially Exponential decay Exponential curve Statistical value for Statistical areas Measuring Infiltration Measuring Precipitation – Runoff = Infiltration Precipitation Assume evaporation = 0 Assume Lecture 13: Surface Water Page 9 of 18 Lecture 13: Surface Water Infiltration vs. Soil Type vs. Soil Fine grained soils Fine (clay) – High initial infiltration – Low equilibrium infiltration Coarse grained soils Coarse (gravel) – Rapidly reaches equilibrium – High equilibrium infiltration Ground Water Recharge Field Capacity vs. Soil Type vs. Soil Soil must reach field Soil capacity Sands have greater Sands recharge Clays have minimal Clays recharge Lecture 13: Surface Water Page 10 of 18 Lecture 13: Surface Water Evaporation Rate Temperature Temperature Relative humidity Relative Wind velocity Wind Water chemistry Water Inversely with salinity Inversely Greatest in fresh water Greatest Surface area Surface Values Time dependant Time Statistical average Statistical Transpiration Rate Vegetation type Vegetation Growing season Growing Temperature Temperature Relative humidity Relative Wind velocity Wind Values Seasonal values Seasonal Statistical averages Statistical Lecture 13: Surface Water Page 11 of 18 Lecture 13: Surface Water Evapotranspiration Sum of Evaporation and Transpiration Sum Difficult to measure Difficult Based upon tables and average values Based Storage Precipitation trapped behind/in: – Dams and lakes – Puddles – Pools – anything that traps water Impossible to determine Impossible Apply statistical average/guess Apply Lecture 13: Surface Water Page 12 of 18 Lecture 13: Surface Water Hydrologic Budget Average Precipitation Lecture 13: Surface Water Page 13 of 18 Lecture 13: Surface Water Evapotranspiration U.S. Moisture Regions Lecture 13: Surface Water Page 14 of 18 Lecture 13: Surface Water Let’s Look at Texas Lecture 13: Surface Water Page 15 of 18 Lecture 13: Surface Water Texas Weather Makers Lecture 13: Surface Water Page 16 of 18 Lecture 13: Surface Water Moisture Index Moisture Index = 100x[(P-PE)/PE] Moisture – P = Precipitation – PE = Potential Evapotranspiration Moisture Extremes Moisture – Arid = <-40 – Perhumid = >+80 Surface Water Law Lecture 13: Surface Water Page 17 of 18 Lecture 13: Surface Water Break Lecture 13: Surface Water Page 18 of 18 Lecture 13: Surface Water ...
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