The Hydrological System. Cintia Bertacchi Uvo

Transcription

1 The Hydrological System Cintia Bertacchi Uvo

2 Learning Goals Hydrological cycle Climate and water availability Catchment area Water balance equation (continuity equation) Runoff coefficient How to calculate pollutant transport out from the project area

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4 Human Activities Source:

5 Water Use and Consumption Global Household Source: World Water Assessment Programme (WWAP, UN-Water)

6 Climate and Water Availability Solar Radiation

7 Atmospheric Circulation

8 Atmospheric Circulation cloud animation

9 Main Deserts of the World Source:

10 Variation in precipitation Monthly precipitation in Lund since 1753 [mm]

11 Water Balance Interception losses (evaporation from leafs, etc.) P Transpiration (from plants) Soil evaporation ΔM Soil water E Groundwater flow Runoff Q

12 Water balance for different climates Swedish boreal forest numbers in mm/year Swedish boreal forest Semiarid steppe Semiarid steppe Tropical rainforest Tropical rainforest

13 Water Balance Equation What comes in has to go out or be stored P Q E = ΔM P E P = precipitation E = evapotranspiration Q = runoff ΔM = change in storage ΔM M Q

14 Examples of water balance calculation For an area the annual precipitation is 1300 mm/year and annual evapotranspiration is 800 mm/year. What is the average runoff if there is no storage during the year? For the same area precipitation was 700 and evapotranspiration 500 mm during 6 months. What was the runoff if the increase in water storage was 100 mm? Remember to ALWAYS use the same the units when doing a water balance (mm/month, mm/day, mm/30 min, )

15 Mean Values of Q, E and P [mm/year]

16 Local water balance

17 Water Balance within an area Commonly Water Balance is made within a catchment area, that is Rainfall collecting area upstream a certain point in the water course

18 Catchment Catchment area is defined by topographical water divide

19 Catchment size 10 6 km 2 Amazon 7 x 10 6 km km 2 Skarsvatn 86 km 2 Bulken 1094 km 2

20 Thousands of sub catchments

21 Runoff Coefficient Ex. 1.1 Two rainfall events, just after one another, falls over a catchment. After the first rainfall of 24 mm, a total runoff of 11 mm was observed. The second rainfall is measured to about 14 mm. How large runoff can be expected after the second rainfall? P Rain 1; Rain 2; P 1 = 24 mm Q 1 = 11 mm P 2 = 14 mm Q 2 =? Q k = Q/P

22 Use of Water Balance Equation Ex. 1.1 A 121 ha large lake has an inflow via a river corresponding to m 3 /s. There is also an outflow from the lake via another river that corresponds to m 3 /s. During one month the water level in the lake increases corresponding to m 3. During the same month it rained 33 mm. How large was the total evaporation from the lake during this month (1 ha = m 2 )? Q in Lake Q out Solution:

23 Water Storage

24 Water Storage Ex. 1.1 For a catchment with an area of 20 km 2 an average of 732 mm/year of precipitation and total evaporation of 550 mm/year has been observed during a 10-year period. Within the catchment there is an old waste dump and in the outflow water high phosphorous (P) contents have been found 0.25 mg/l P. What is the annual mass transport of phosphorous in the water out from the catchment? P - E - Q = ΔM P E Q, C A = 20 km 2 P = 732 mm/year E = 550 mm/year C = 0.25 mg/l P