Final answer:
The estimated annual water balance of the watershed is a deficit of 466 mm/year. This is calculated by subtracting the total annual water output (1616 mm/year, including streamflow out, groundwater flow out, and evapotranspiration) from the total annual water input (1150 mm/year, including precipitation and groundwater flow in).
Step-by-step explanation:
To estimate the annual water balance, or budget, for a watershed, we consider all inputs and outputs of water. The given values are:
- Annual precipitation: 800 mm
- Annual streamflow out: 450 mm
- Annual groundwater flow in: 350 mm
- Monthly groundwater flow out: 85 mm
- Daily evapotranspiration: 0.4 mm
First, let's calculate total annual outputs by considering streamflow, groundwater flow out, and evapotranspiration. To convert daily evapotranspiration to annual, we multiply by 365 days:
Annual evapotranspiration = 0.4 mm/day × 365 days/year = 146 mm/year
Next, we convert monthly groundwater flow out to annual by multiplying by 12 months:
Annual groundwater flow out = 85 mm/month × 12 months/year = 1020 mm/year
Now, we can add all outputs:
Total annual water output = Streamflow out + Groundwater flow out + Evapotranspiration = 450 mm + 1020 mm + 146 mm = 1616 mm/year
The total annual input is just the sum of annual precipitation and groundwater flow in:
Total annual water input = Precipitation + Groundwater flow in = 800 mm + 350 mm = 1150 mm/year
To find the water balance, we subtract the total output from the total input:
Annual Water Balance = Total input - Total output = 1150 mm/year - 1616 mm/year = -466 mm/year
The negative water balance suggests that the watershed has a deficit of 466 mm/year.