1. 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

2. Hydrologic Cycle

3. 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

4. Digital Atlas of the World Water Balance (Precipitation)

5. 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

6. Global Water Resources
105,000 km3 or % of total water

8. 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 )
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 = yr = 8.2 days
One reason why weather cannot be forecast accurately more than a few days ahead!

9. Population and Water Use
global freshwater use is ~4000 km3/year
~10% of the renewable supply (44,800km3/year)

10. Global Water Availability
500
1350
3850
10000
37500
325000

11. Watershed system

12. 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”

13. Texas Surface Water
Colorado River

14. Aquifers in Texas

15. Homework 1– How much water is there in Texas?
Category
Area (km2)
Volume, V (km3)
Standard Error Estimate of V
Atmospheric water
Biological water
Rivers
Reservoirs
Small lakes and farm ponds
Marshes
Estuaries
Soil water
Groundwater - fresh
Groundwater - saline

16. 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)