Hydrologi och akvatisk ekologi Läsperiod 1Ex 1, For an area the annual precipitation is 1300...
Transcript of Hydrologi och akvatisk ekologi Läsperiod 1Ex 1, For an area the annual precipitation is 1300...
Hydrological system
Learning goals:
- hydrological cycle- climate and water availability- catchment area- water balance equation (continuityequation)- runoff coefficient- how to calculate pollutant transport out from the project area
Hydrological cyclecomponents and turnover
time1 week
1 week -10 years
5000 years
8000 years
3000 years
Global water distribution
Atmosphere 0,001%Lakes, rivers, creeks 0,009%
Groundwater, soil 0.615%Ice caps, glaciers 2,04%
Oceans, saltwater lakes 97,31
Atmospheric flow decideswhere water availability is
large or small
Sun energy
Precipitation
Precipitation
No precipitation
No precipitation
Precipitation
Gulf stream suppliesNorthern Europe with 50%
of available heat
Direct sun insolation remaining 50% of the heat
Water balances
P
E
Q
ΔM
WATER FLOWS
Interception losses (evaporation from leafs, etc
Transpiration (from plants)
Soil evaporation Runoff
Soil water Groundwater flow
Storage changes ΔM approx. constant seen over
1 year!
spring spring
ΔM
Q
Lake water, snow, groundwater, soil water
1 year
Example water balancecalculations
Ex 1, For an area the annual precipitation is 1300 mm/year and annual evaporation is 800 mm/year. What is the average runoff?
Ex 2, For the same area precipitation was 700 and evaporation was 500 mm during 6 months. What was runoff if the increase in water storage was 100 mm?
Catchment area is definedby topographical water
divide
Catchment = rainfall collectingarea upstream a certain point in the water course.
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Remember: always use the same unit in the water balance equation;
for example mm/year, mm/month, m3/s,
Ex. A 1 ha catchment has received 100 mm rainfall during a month. During the same month runoff was 0.1157 l/s and storagechanges equal to zero. What was the evaporation during the month?
Ex. 2.1, Two rainfall events, just after one another, fall 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
Q
Rain 1; P1 = 24 mm Q1 = 11 mm Rain 2; P2 = 14 mm Q2 = ?
Ex. 2.2, A 121 ha large lake has an inflow via a river corresponding to 0.425 m3/s. There is also an outflow from the lake via another river that corresponds to 0.368 m3/s. During one month the water level in the lake increases corresponding to 19.7 · 103 m3. During the same month it rained 33 mm. How large was the total evaporation from the lake during this month (1 ha = 10 000 m2)?
Lake Qout
Qin
Ex. 2.3, For a catchment with an area of 20 km2 an average of 732 mm/year of precipitation and total evaporation of 550 mm/year have 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?
Solution: Put up a water balance for the catchment. That is
P - E - Q = ΔM
A = 20 km2 P = 732 mm/year E = 550 mm/year C = 0.25 mg/l P
P
Q, C
E