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CE 394K.2 Hydrology – Lecture 1. Syllabus, term paper, sequence of topics Hydrologic cycle and world water balance Water quantities in Texas Readings: For today – Applied Hydrology, Chapter 1 For Tuesday – AH, Sections 2.1 and 2.2.
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CE 394K.2 Hydrology – Lecture 1 • Syllabus, term paper, sequence of topics • Hydrologic cycle and world water balance • Water quantities in Texas Readings: • For today – Applied Hydrology, Chapter 1 • For Tuesday – AH, Sections 2.1 and 2.2 Some slides in this presentation were prepared by Venkatesh Merwade
Global water balance (volumetric) Precipitation 100 Atmospheric moisture flow 39 Precipitation 385 Evaporation 424 Evaporation 61 Surface Outflow 38 Land (148.7 km2) (29% of earth area) Ocean (361.3 km2) (71% of earth area) Subsurface Outflow 1 Units are in volume per year relative to precipitation on land (119,000 km3/yr) which is 100 units
Digital Atlas of the World Water Balance(Precipitation) http://www.crwr.utexas.edu/gis/gishyd98/atlas/Atlas.htm
Global water balance (mm/yr) Precipitation 800 Atmospheric moisture flow 316 Precipitation 1270 Evaporation 1400 Evaporation 484 Outflow 316 Land (148.7 km2) (29% of earth area) Ocean (361.3 km2) (71% of earth area) What conclusions can we draw from these data? Applied Hydrology, Table 1.1.2, p.5
Global Water Resources 105,000 km3 or 0.0076% of total water
Residence Time Residence time: Average travel time for water to pass through a subsystem of the hydrologic cycle Tr = S/Q Storage/flow rate Residence time of global atmospheric moisture (Ex. 1.1.1) Volume (storage) of atmospheric water: 12,900 km3 Flow rate of moisture from the atmosphere as precipitation = 577,000 km3/yr Tr= 12,900/577,000 = 0.022 yr = 8.2 days One reason why weather cannot be forecast accurately more than a few days ahead!
Population and Water Use global freshwater use is ~4000 km3/year ~10% of the renewable supply (44,800km3/year)
Global Water Availability 500 1350 3850 10000 37500 325000
Hydrologic System Take a watershed and extrude it vertically into the atmosphere and subsurface, Applied Hydrology, p.7- 8 A hydrologic system is “a structure or volume in space surrounded by a boundary, that accepts water and other inputs, operates on them internally, and produces them as outputs”
Texas Surface Water Colorado River
Standard Error of Estimate Statistical average, estimates mean m Standard deviation, estimates s Standard error of estimate (SEE) of the mean m is Provided all samples xi are statistically independent of each other (see Applied Hydrology Section 11.1 for definition of independence)