You're studying the groundwater flow rate in your catchment. Use the data below to estimate the Darcian flow rate (in unit of m^2)

• Groundwater bore 1 land surface elevation = 106 m above sea level.
• Groundwater bore 2 land surface elevation = 62 m above sea level.
• Depth to the groundwater at bore 1 = 10.3 m.
• Depth to the groundwater at bore 2 = 8.8 m.
• Distance between the two bores = 1094 m.
• Aquifer conductivity = 1.9 m/day
• Aquifer thickness = 14 m

A small township is down stream of a major lake and the residence are concerned that the lake may overflow soon. 

Using the lake bucket model below (week 4) estimate the lake overflow (as mm) at the end of the day.

\frac{dS}{dt} = \frac{A_{catchment}} {A_{lake}} * f * P - E

Catchment properties:

• Catchment area, A_{catchment} of 11 km^2
• Lake area, A_{lake}, of 2 km^2
• Initial storage of lake 3870 mm

• Maximum storage of lake 4009 mm

• Fraction of rainfall to streamflow, f

  , of 0.31

• Average evaporation, E, of 4.3 mm/day
• Rainfall over the day, P

  ,  of 64 mm/day

Use the following catchment mass balance equation and observations to estimate the mean evaporation.

\frac{dS}{dt} = P - Q - E

where S is the catchment water storage, P is the annual rainfall, Q is the annual streamflow and E is the catchment evaporation.