Whitney Kihlstrom
Task 1. Calculate monthly soil water store of Pahang Tenggara, Malaysia
Monthly meteorological data for Pahang Tenggara, Malaysia.Month / ΣP∆t Rainfall (in) / ∆e Vapour Pressure (Hg) / ΣE∆t Evaporation (in)
1 / 7.3 / 0.49 / 5.9
2 / 7.7 / 0.51 / 6.1
3 / 9.0 / 0.59 / 6.9
4 / 8.7 / 0.59 / 6.9
5 / 8.2 / 0.55 / 6.5
6 / 5.1 / 0.53 / 6.3
7 / 5.8 / 0.53 / 6.3
8 / 6.7 / 0.53 / 6.3
9 / 7.7 / 0.55 / 6.5
10 / 12.6 / 0.50 / 6
11 / 13.6 / 0.40 / 5
12 / 13.1 / 0.37 / 4.7
Monthly meteorological data for Pahang Tenggara, Malaysia.
Month / Σ(P-E)∆t Evapotranspiration (in) / S + U Surface Runoff and Drainage (in) / Mt Soil Water Store (in)
1 / 1.4 / 1.4 / 5
2 / 1.6 / 1.6 / 5
3 / 2.1 / 2.1 / 5
4 / 1.8 / 1.8 / 5
5 / 1.7 / 1.7 / 5
6 / -1.2 / 0 / 3.8
7 / -0.5 / 0 / 3.3
8 / 0.4 / 0 / 3.7
9 / 1.2 / 0 / 4.9
10 / 6.6 / 6.5 / 5
11 / 8.6 / 8.6 / 5
12 / 8.4 / 8.4 / 5
Task 2. Calculate annual runoff ratios of the Coweeta Hydrological Laboratory, NC.
Good.
No brief description about the seasonal variation of soil water store such as soil moisture deficit or surplus.
Assumption
No vertical or surface runoff until soil water overflows over the bucket. In reality, most watersheds are leaky, which means that we have quite a mount of streamflow even during dry seasons.
AET is equal to pan evaporation. But, in fact AET is lower than pan evaporation in most seasons maily because of the shortage of soil water supply.
No brief description about the seasonal variation of soil water store such as soil moisture deficit or surplus.
1/3
Q 2-1
Mean (RR) = 0.5015
Std (RR) = 0.0995
Std/Mean = 0.1984
The ratio of standard deviation to mean is called a coefficient of variation, which represents the relative variation of a variation, normalized by its magnitude.
2/2
Q 2-2
As the annual precipitation increases, the annual runoff ratio tends to increase as demonstrated by the linear regression line. This is due to the fact that once the land is saturated, no more precipitation can infiltrate. Therefore, the more precipitation, the more runoff once the land is saturated. Spatial expansion of saturated area is one reason.
In addition, consider the effects of soil water content on the generation of surface runoff. As precipitation increases, soils tend to be wetter, which means the decline of infiltration capacity. As a result, more portion of precipitation flows out as surface runoff without infiltrating into soils.
1.7/2
Q 2.3
The previous results suggest that annual runoff ratios are not an intrinsic property of a watershed, as the value does not stay relatively constant over time. The annual runoff ratio depends on many parameters, including total precipitation, infiltration rates, and antecedent soil moisture conditions. The plot of annual runoff ratios from 1940 to 2002 displays considerable variation between some years. For instance, runoff ratio for 1989 is 0.4513 while that of 1990 is 0.6767, a difference of more than 0.2. The plot of annual runoff ratios versus annual precipitation demonstrates that runoff ratios increase with precipitation. Because precipitation values differ from year to year, this data does not suggest that the annual runoff ratio is an intrinsic hydrologic property of a watershed. 2/2
Q 2.4
In theory, pan evapotranspiration should be higher than the annual precipitation minus the annual stream discharge. This is due to the fact that an increase in water temperature is associated with the pan method of measurement, resulting in higher evapotranspiration. However, as seen below, pan evapotranspiration measurements for WS18 are often lower than that calculated by subtracting the annual steam discharge from the annual precipitation. Therefore, this data does not support the argument that the water budget equation of WS 18 can be simplified so that the annual actual evapotranspiration of the watershed may be approximated to the difference between the annual precipitation and the annual stream discharge. This simplification assumes homogeneous land cover, i.e. type of vegetation and stage of growth. It also assumes a homogenous amount of precipitation throughout the area, which is not always true of a given watershed.
Since the area has a deep weathered saprolite underground structure, we expect there is significant deep groundwater flow, bypassing a weir to measure stream discharge. So, in reality, AET can be much lower than P-Q.
1.5/3
Why don’t you plot the following table?
P-Q (mm) / Epan (mm) / Year966 / 880 / 1940
725 / 924 / 1941
1048 / 916 / 1942
916 / 888 / 1943
905 / 919 / 1944
917 / 941 / 1945
975 / 899 / 1946
879 / 886 / 1947
1008 / 828 / 1948
1013 / 828 / 1949
808 / 775 / 1950
841 / 842 / 1951
787 / 909 / 1952
960 / 968 / 1953
829 / 890 / 1954
1139 / 860 / 1955
937 / 859 / 1956
1009 / 902 / 1957
904 / 762 / 1958
927 / 856 / 1959
889 / 845 / 1960
857 / 838 / 1961
700 / 855 / 1962
953 / 919 / 1963
879 / 971 / 1964
821 / 896 / 1965
877 / 884 / 1966
973 / 887 / 1967
628 / 932 / 1968
1056 / 907 / 1969
773 / 996 / 1970
952 / 932 / 1971
853 / 915 / 1972
811 / 893 / 1973
919 / 886 / 1974
896 / 817 / 1975
676 / 847 / 1976
874 / 855 / 1977
622 / 895 / 1978
991 / 936 / 1979
570 / 935 / 1980
812 / 848 / 1981
947 / 905 / 1982
757 / 902 / 1983
831 / 906 / 1984
913 / 836 / 1985
603 / 938 / 1986
1104 / 849 / 1987
717 / 917 / 1988
1203 / 842 / 1989
656 / 925 / 1990
867 / 792 / 1991
961 / 832 / 1992
613 / 899 / 1993
1142 / 831 / 1994
830 / 877 / 1995
984 / 825 / 1996
730 / 909 / 1997
608 / 897 / 1998
939 / 971 / 1999
879 / 925 / 2000
1095 / 843 / 2001
919 / 891 / 2002
Task 3. Estimate effects of climate change on runoff
The relative increase of runoff of the CoweetaBasin when the precipitation increases by 20% and evapotranspiration increases by 10% is approximately 90%. This value is found by taking the runoff ratio (w) to be the mean runoff ratio from 1940 to 2002 (0.5015).
Something wrong.
so the relative increase of runoff is 29.9%.
1.5/3
Task 4. Readings
The Gravity Recovery and Climate Experiment (GRACE) consists of two satellites, one approximately 220 km ahead of the other on identical orbits. The first satellite observes small changes in gravity, which pulls the satellite closer to Earth and thus further from the second satellite. Range finders measure the distance between the two satellites, allowing extremely precise measurements of gravity to be made. This will result in a map “100 times more accurate than the best previous effort” (Amazing GRACE) every thirty days. This method is unique because it is able to penetrate oceans depths previously unreachable. Also, it is extremely sensitive to subtle changes and is updated much more frequently than prior gravity measurements. Changes in Earth’s gravity are related to changes in mass distribution, including water. Therefore, this information can be applied to water budgets in large river basins. GRACE will allow more accurate measurement of water in the soil column, thus better measurement of soil water content and therefore runoff ratios. Be more specific in potential applications including snow-melt, or flooding.
Using a water balance equation, we can also estimate ET of the whole river basin.
2.5/3
Total:
12.2/18= / 6.8