Response to the following question:
1. The Colorado River water has an EC of 1.25 dS/m (1 dS/m is approximately equivalent to 700 mg/l). Calculate how much salt is added to a field of 1 Ac during a year if the total irrigation for crop production for the year is 5 ft (hint: unit conversion!).
2. The rainfall intensity during a 9-hour period is 6 mm/hour (constant). The soil infiltration rate can be described by
i (mm/h) = 2 t-0.5 + 4.0 (where t is in hour)
Estimate the total runoff during the 9-hour period (hint: runoff only occurs after the surface is under ponding. Time of ponding is calculated by setting infiltration rate equal to rainfall intensity).
3. A reservoir with 200 Ac of surface area receives 100 cfs of overland flow and 10 cfs of groundwater flow. In the mean time, it discharges 90 cfs to the outlet channels to maintain the downstream ecosystem balance. The average evaporation loss is 0.2 in/d. The ground seepage is estimated to be 15 cfs. Determine if the reservoir is losing or gaining water.
4. A 100 cm soil column containing sand of saturated hydraulic conductivity KS = 100 cm d-1 has 10 cm of water continuously ponded over it. The bottom is open to the atmosphere. Calculate the steady flux through the column.