The Economic Value of Water and Ecosystem Preservation

Based on the regression results, a simplified equation was formulated to
estimate visitors over a range of flow levels. The equation is given as follows:
2
Equation 2: V i = 2.
157Qi
− 0.
00047Q
i + 2264
The variable V represents the monthly visitor number and Q is the average
monthly inflow. Figure 4-5 illustrates the modeled impact of freshwater inflows on
visitor numbers.
Figure 4-5. Modeled relationship of freshwater inflows to visitor numbers
Visitors (Persons)
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0
0 1000 2000 3000 4000 5000 6000
Figure 4-5 shows increasing visitors for freshwater inflows increasing to an
inflow rate of 2,400 cfs; whereas, the average monthly flow rate was calculated
from USGS statistics as 1,995 cfs. Equation 2 yields an estimate of 4,714 visitors
for the average monthly flow rate. Multiplying the estimated number of visitors
with the average expenditures as reported in the travel cost data ($508) yields a
total travel expenditure of $2.39 million. An incremental increase of 100 cfs is
modeled as an increase of 25 visitors for an incremental increase of $12,700 in
eco-tourism expenditures. Assuming a 30 day month, 100 cfs converts to 22,442
42
Flow (cfs)