Lecture3 hydrology cycle dung

VFU-2016 Lecture #3 Hydrological cycling Principles of Watershed management Dr Bui Xuan Dung- Department of Environment Management Components of Earth’s water Earth's Water and the Hydrologic Cycle Supply of Water Resources Small fraction (.014%) is readily available for human use HYDROLOGY | fresh water HYDROLOGY | fresh water | rivers & lakes Hydrologic cycle The processes and pathways involved in the circulation of water from land and water bodies to the atmosphere and back again Changes in the formation of H2O (Ice, liquid, gas) Components of Earth’s water Earth's Water and the Hydrologic Cycle What is significant of hydrology cycle? Watershed Precipitation How well the gauges in a watershed represent the precipitation over the entire watershed area? Excercise PA = 1,9 in; PB = 2,5 in; PC= 3,0 in; PD = 3,2 in Please calculate watershed precipitation using Thiessen method Number square of AA=66, AB=86, AC=134, AD=50 Need to predict probability of different events (floods, storms, etc.)  10-year, 1-hour rainstorm;  100-year flood;  Likelihood of receiving less than 1000 mm of annual precipitation leading to crop failure or shortage of water supply; Frequency Analysis for Precipitation For watershed management, we need to design and plan for future event Weather system vary from one year to the next (also seasonally) Statistical analysis of rainfall amount over certain period Calculation for Frequency curve Predicting probability of a given event Take a series of data: - Most common is annual maximum (most extreme event in a year); - Can use annual totals, daily values, 7day minimum, or almost any time series; Annual Precip for LA, CA 1934-1953 Year Depth (in) 1934 14.6 1935 21.7 1936 12.1 1937 22.4 1938 23.4 1939 13.1 1940 19.2 1941 32.8 1942 11.2 1943 18.2 1944 19.2 1945 11.6 1946 11.6 1947 12.7 1948 7.2 1949 8.0 1950 10.6 1951 8.2 1952 26.2 1953 9.5 Predicting probabilities   Rank from largest to smallest (floods and storms), or smallest to largest (droughts); Each data point must have a different rank, even if the data are the same;  This helps indicate that the probability for a given value is uncertain! Table 2.6 Annual Precip for LA, CA 1934-1953 Year Depth (in) Rank Depth (in) Year 1934 14.6 32.8 1941 1935 21.7 26.2 1952 1936 12.1 23.4 1938 1937 22.4 22.4 1937 1938 23.4 21.7 1935 1939 13.1 19.2 1940 1940 19.2 19.2 1944 1941 32.8 18.2 1943 1942 11.2 14.6 1934 1943 18.2 10 13.1 1939 1944 19.2 11 12.7 1947 1945 11.6 12 12.1 1936 1946 11.6 13 11.6 1945 1947 12.7 14 11.6 1946 1948 7.2 15 11.2 1942 1949 16 10.6 1950 1950 10.6 17 9.5 1953 1951 8.2 18 8.2 1951 1952 26.2 19 8.0 1949 1953 9.5 20 7.2 1948 Predicting probabilities  Calculate probability for each event by plotting position formula   Most common is p = m/(n + 1) where m is rank and n is number of years; We add one to the number of data points because a more extreme event can always occur, and we can’t have 100% probability of anything! Annual Precip for LA, CA 1934-1953 Year Depth (in)Rank Depth (in) Prob 1934 14.6 32.8 2.5 1935 21.7 26.2 7.5 1936 12.1 23.4 12.5 1937 22.4 22.4 17.5 1938 23.4 21.7 22.5 1939 13.1 19.2 27.5 1940 19.2 19.2 32.5 1941 32.8 18.2 37.5 1942 11.2 14.6 42.5 1943 18.2 10 13.1 47.5 1944 19.2 11 12.7 52.5 1945 11.6 12 12.1 57.5 1946 11.6 13 11.6 62.5 1947 12.7 14 11.6 67.5 1948 7.2 15 11.2 72.5 1949 8.0 16 10.6 77.5 1950 10.6 17 9.5 82.5 1951 8.2 18 8.2 87.5 1952 26.2 19 8.0 92.5 1953 9.5 20 7.2 97.5 Same values get different ranks and probabilities! Drawing Frequency curve Amount of Precipitation n 1 Tr   m p Tr: Recurrence Interval Amount of Precipitation (yr) Recurrence Interval of Precipitation (yrs) or Probability n: number of years m: rank of the event Recurrence Interval (yr) A measure of how often-on average-an event of this magnitude OR a more extreme event will occur Example (Oume AMeDAS station) Automated Meteorological Data Acquisition System Year 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Annual 1423 1660 1003 1596 1294 1343 1755 1328 858 1489 1500 992 1556 1716 1659 2233 1717 1405 1305 1157 1069 1107 2226 1718 1443 1443 1664 1784 1429 1425 1593 Max 24 hr 80 152 66 173 57 140 228 101 61 128 152 68 79 103 195 159 119 104 127 65 150 101 189 274 102 116 192 92 167 140 125 Year 1999 1982 1990 2002 1998 1979 2004 1991 1977 1986 1996 1981 2005 1985 1994 2006 1992 2001 1993 1989 2000 1983 1997 2003 1976 1988 1987 1978 1995 1984 1980 Max 24hr rain Rank 274 228 195 192 189 173 167 159 152 152 150 140 140 128 127 125 119 116 104 103 102 101 101 92 80 79 68 66 65 61 57 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 n 1 Tr  m Recurrence Interval 32.00 16.00 10.67 8.00 6.40 5.33 4.57 4.00 3.56 3.20 2.91 2.67 2.46 2.29 2.13 2.00 1.88 1.78 1.68 1.60 1.52 1.45 1.39 1.33 1.28 1.23 1.19 1.14 1.10 1.07 1.03 Frequency curve year recurrent interval event is approximately 165 mm/24hrs Max 24 hr precipitation (mm) 300 200 mm/24hrs event is approximately 12 year recurrence interval 250 200 150 100 50 0 10 15 20 25 Recurrence Interval (yrs) 30 35 Commonly Used Units and Dimensions for Water in Watershed •Rainfall (total or accumulated): mm (for snow depth – m) •Rainfall (intensity): mm/h Catchment area: ha; km2 = 10,000 m2 km2 = 100 ha = 0.01 km2 •Volumetric Flow or Discharge: m3/s •Volumetric flow or Discharge (groundwater well production): l/s; l/min; l/h; l/day •Streamflow or Discharge per unit area (sometimes called ‘specific or unit discharge’): m3/s per km2 •Volume of Flow: Large volumes - m3 Small volumes- liter (l) •1 liter = 0.001 m3 •Flow velocity: m/s ... the Hydrologic Cycle Supply of Water Resources Small fraction (.014%) is readily available for human use HYDROLOGY | fresh water HYDROLOGY | fresh water | rivers & lakes Hydrologic cycle The processes... (Ice, liquid, gas) Components of Earth’s water Earth's Water and the Hydrologic Cycle What is significant of hydrology cycle? Within 2.6 % of Freshwater on the earth Approximately Only 12 % of Freshwater: