地下水文学计算题

1. A confined aquifer is 18.5m thick. The potentiometric surface elevations at two observation wells 822m apart are 25.96 and 24.62m. If the horizontal hydraulic conductivity of the aquifer is 25m/d, determine the flow rate per unit width of the aquifer, specific discharge, and average linear velocity of the flow assuming steady unidirectional flow.

2. A unconfined aquifer in a stratum of clean sand and gravel has a hydraulic conductivity of 0.01cm/sec. From two observation wells 200m apart, the observed water table elevations are 11 and 7m measured from the bottom of the stratum. Determine the discharge per unit width of the aquifer.

3. A unconfined aquifer of clean sand and gravel is located between two fully penetrating rivers, and has a hydraulic conductivity of k=0.01cm/sec. The aquifer is subject to a uniform recharge of 1.6m/year. The water surface elevations in rivers A and B are 8.5m and 10m, respectively, above the bottom. Estimate (a) the maximum elevation of the water table and the location of groundwater divide, (b) the travel times from groundwater divide to both rivers(ne=0.35), and (c) the daily discharge per kilometer from the aquifer into both rivers.

4. Two observation wells have been constructed in the unconfined aquifer shown below and the piezometric heads in the wells are 13m and 10.5m respectively. If the flow rate q is 0.02 m3/hr/unit width, determine K2?

5. Following figure demonstrates a stratified material in an alluvium. Hydraulic conductivity and specific yield for the upper layer are 5.5m/d and 0.1, respectively. Thickness of the lower layer M is 33m, with a hydraulic conductivity of 10.8m/d. River stages in the both sides of the aquifer keep steady, and they are 97.5m and 89m for rivers A and B, respectively. The distance between the both rivers is 1.2km. The river length is 7km. If the precipitation recharge and groundwater evaporation loss are ignored, we would like to know:

（1）The total water flowing from the left river to the right river in 30 days.

（2）Water storage amount in the upper aquifer.

（3）From a time t0, river stages vary in mathematical functions g A(t), g B(t) for rivers A and B, respectively. Express the Governing equation, Boundary Conditions, and Initial Conditions of the mathematical model.

6. A well that pumps at a constant rate of 0.5m3/s fully penetrates a confined aquifer of 34m thickness. After a long period of pumping, near stead state condition, the measured drawdowns at two observation wells 50 and 100m from the pumping well are 0.9 and 0.4m, respectively.

(a) Calculate the hydraulic conductivity of the aquifer,

(b) estimate the radius of influence of the pumping well, and

(c) calculate the expected drawdown in the pumping well if the radius of the well is

0.4m.

7. A pumping well of 0.5m diameter fully penetrates a unconfined aquifer produces at a constant rate of 80m3/hr, the initial water table is 33m. After a long period of pumping, near stead state condition, the drawdown in a observation well 18m from the pumping well is 1.8m. The drawdown in another observation well 45m from the pumping well is 1.1m.

(a) Calculate the hydraulic conductivity of the aquifer,

(b) the expected drawdown in the pumping well, and

(c) the radius of influence of the pumping well.