Tutorial 1A

Department of Geography and Environmental Management GEOG 303 University of Waterloo Notes: 1km = 10 3 m = 10 5 cm = 10 6 mm 1 m 3 = 10 3 litre With those concepts in mind, answer to the following exercises: 1) Consider that the hypothetical town of Geog303 is located inside a watershed with an area of approximately 4200 km 2 . Annually, the watershed receives an average precipitation of 825 mm. Part of the precipitation flows as surface water and converges into creeks that are tributaries to the main river of the watershed. The outlet of the watershed is located where the main river meets a reservoir, and the river discharge at that point is 1.83x10 9 m 3 year -1 . Another part of the precipitation ends up infiltrating the soils in the watershed, which eventually percolates into deeper layers of the ground, reaching the water table and recharging local groundwater. In turn, groundwater slowly flows into the downstream reservoir. Annually, the watershed experiences an outflow of groundwater of nearly 80 mm year -1 . All averages were calculated based on 30 hydrological years. a) Considering that there is no change in storage: a1) Define the ins and outs of the water balance equation in this watershed. (0.5 marks) a2) Calculate the amount of evapotranspiration in mm year -1 and in m 3 year -1 . (1 mark) b) Now, considering that evapotranspiration is 9.2x10 8 m 3 year -1 . b1) Calculate the change in storage in mm. (1 mark) b2) Over the last 30 hydrological years, did this watershed had a gain or a loss in water storage? (0.5 marks) 2) Now, let’s think about the water balance within the hillslope scale. The hillslope has an area of approximately 2x10 -2 km 2 . During a rainfall with an average intensity of 10 mm hour -1 and duration of 90 minutes, surface runoff (produced over the 90 minutes) is approximately 2.1x10 5 litres. If evapotranspiration and groundwater components are negligible, how much water (in mm and m 3 ) is stored in the soil as soil water in this 90-minute precipitation event? (2 marks)