VOLUSIA BLUE SPRING – DECLINING FLOW

Dingbao Wang and Jonathan Griffen

The University of Central Florida’s Walter and Betty Boardman Foundation contracted with Dr. Dingbao Wang, Assistant Professor at the University of Central Florida, to explore the causes for the decline in flow at Volusia Blue Spring.

Summary
Blue Spring has been experiencing a decline in discharge since 1976. From 1976 to 2012, the annual average discharge decreased from 152 ft3/s to 127 ft3/s.  Precipitation trends were analyzed for a possible explanation of the declining discharge, but no significant decreasing trend was observed.  Increasing evaporation rates were another factor considered. Due to the limited evaporation data, temperature trends, which correlated fairly well with the available evaporation data, were used as an approximation of evaporation and extended the analysis prior to 1983. From this record, it was observed that the temperature trend did not correlate closely with the discharge trend. Starting about 1952, the temperature had been on a declining trend, which ended around 1989 and began to increase in 2002.  Discharge, on the other hand, had been on a declining trend since 1976.  That is, though increasing evaporation rates may have had some impact on the declining discharge, it is likely not the primary cause of the trend.

From the population and water use data it is evident that human activities have had a significant impact on the springshed, especially around the 1970’s, as demonstrated by the change in land use which resulted in a loss of wetlands and an increase in urban area.   As indicated in the land use data, water use data, and population data, a significant increase in the impact of human development on the springshed was observed. First, there was a 61% increase in total water use for the springshed from 1965 to 1975, which accelerated to a 58% increase from 1975 to 1980 (which is nearly the same rate in half the time). Also, there was a significant increase in the population growth rate beginning in 1950 and then especially after 1970.  Finally, there was a significant increase in the urban area, particularly from 1973 to 1995 (31.1%).