The Hydrological System Cintia Bertacchi Uvo
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
Human Activities Source: http://www.unep.or.jp/ietc/publications/short_series/lakereservoirs-2/9.asp
Water Use and Consumption Global Household Source: World Water Assessment Programme (WWAP, UN-Water)
Climate and Water Availability Solar Radiation
Atmospheric Circulation http://schoolworkhelper.net/
Atmospheric Circulation cloud animation
Main Deserts of the World Source: http://pubs.usgs.gov/gip/deserts/what/world.html
Variation in precipitation Monthly precipitation in Lund since 1753 [mm]
Water Balance Interception losses (evaporation from leafs, etc.) P Transpiration (from plants) Soil evaporation ΔM Soil water E Groundwater flow Runoff Q
Water balance for different climates Swedish boreal forest numbers in mm/year Swedish boreal forest Semiarid steppe Semiarid steppe Tropical rainforest Tropical rainforest
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
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, )
Mean Values of Q, E and P [mm/year]
Local water balance
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
Catchment Catchment area is defined by topographical water divide
Catchment size 10 6 km 2 Amazon 7 x 10 6 km 2 10 2 km 2 Skarsvatn 86 km 2 Bulken 1094 km 2
Thousands of sub catchments
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
Use of Water Balance Equation Ex. 1.1 A 121 ha large lake has an inflow via a river corresponding to 0.425 m 3 /s. There is also an outflow from the lake via another river that corresponds to 0.368 m 3 /s. During one month the water level in the lake increases corresponding to 19.7 10 3 m 3. During the same month it rained 33 mm. How large was the total evaporation from the lake during this month (1 ha = 10 000 m 2 )? Q in Lake Q out Solution:
Water Storage
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