IMPACTS ON GROUNDWATER

Transcription

1 CLIMATE CHANGE IMPACTS ON GROUNDWATER RECHARGE: FLORIDA Frederick Bloetscher, Ph.D., P.E. Asst. Professor, Florida Atlantic University Tara M. Bardi, Geologist, GMW&A, West Palm Beach, Florida

2 A Sustainable World: AWWA : The planning, development and management of water resources to provide an adequate and reliable supply of water with a quality suitable to meet their economic, environmental and social needs for current and future generations, And use of resources by our generation in a manner that will not diminish the ability of future generations to meet their needs. Murley (2006)

3 Are Sustainability of Water Supplies and Climate Change Compatible? If recharge is significantly ifi affected, what can we do?

4 Gulf Coast Ecoregions Freshwater wetlands and aquatic ecosystems swamps, freshwater marshes, lakes, rivers, and springs Coastal and nearshore marine ecosystems barrier islands, mangroves & salt marshes, seagrasses, estuaries & bays, and coral reefs

5 It rains in Florida, usually: 50 to 60 inches of rain a year

6 Historical SE Florida Water System

7 Lake Okeechobee Flow 0 The Historical Biscayne Aquifer Conclusion: Atlantic Ocean the Everglades Recharges the -2Biscayne Aquifer (surficial) Biscayne Aquifer 93% of Florida s water is acquired from groundwater

8 Florida s Hydrologic Cycle 66 BGD to tide!!

9 Yet South Florida is Home to 5 M people and counting The Everglades Agriculture (sugar cane and row vegetables) of average rainfall Tropical climate And a Drought

10 From Swamp to Development Goldmine to Sustainable World? To Improve Florida with the major intent being to lower groundwater levels, l the Corps and water control districts : Engaged in the berming of Lake Okeechobee Built 1,800 miles of canals and levees 200 water control structures 16 major pump stations--- including the largest in the world

11 What s the Modern System and how might it affect recharge? Development + Agriculture Faster runoff Faster runoff Less percolation and greater ET

12 Canal bank Canal bank Water level In canal Water level In canal Water level in Aquifer Water flow into canal draining aquifer Water level in Aquifer Because canal and aquifer levels are similar no water flows into canal draining aquifer Associated Issues: Depleting the aquifer Saltwater intrusion Drought Lack of reservoirs Lake Okeechobee nightmare Canals for flood protection ---can also be used to prevent flows out of the aquifer and into the canals--- when there is enough water--but only near the western wellfields, leaving the eastern well fields poorly protected and vulnerable to saltwater intrusion 93% of Florida s water supplies are from groundwater Surface Water Groundwater

13 We Do Have Places that Recharge a lot

14 CF FS in runoff Pre-development Quantity Post Development Quantity Development Means Faster Runoff Hours

15 Huge wetland loss

16 We get a lot of heat which may alter rainfall: Summer The changes in temperature extremes of summer and winter over 24 hrs 1900 vs 1995 Attributed in part to wetland losses; with just one effect of Citrus and Winter Orange counties no longer producing as much citrus as they have historically because they get too many freezes. The Town of Frostproof is NOT anymore 1973 to 1990 (marshall, et al)

17 Changes in Rainfall? 1973 to 1990 (marshall, et al) Note convective rainfall decreases which means the rain has decreased during summer ~12%

18 Convective storm activity ii tends to be most affected There is evidence that land cover and land use changes from 1900 to date and their effects on the convective rainfall, driven by thermal properties between the land and the adjacent ocean, accounts for the reduction in average summer rainfall of 12% which is when 70% of the rain falls

19 Rainfall Change in average rainfall and temperature Note the reverse trend--indicating groundwater inputs are lessened Temperature Marshall, et al 2003

20 Agriculture will argue that irrigation contributes to recharge Even if water percolates beneath the surface not all potential recharge becomes actual recharge. Agricultural practices may actually increase baseflow in rivers rather than contribute to the recharge of the aquifer. The rate at which water filters through the vadose zone is controlled by interactions between soil, water, and plant systems. This rate can increase with changes in precipitation and temperature like those that climate change is expected to manifest, but this does not seem to be as applicable to South Florida which suggests thatwater thatevades evapotranspiration, percolates intothe the ground and is discharged to a stream provides little long term benefit for groundwater recharge. These effects can result from our perennial cropping and high irrigation rates (McGinnis 2007) (Green et al 2006) (Miller et al 1981)

21 So What We know. Direct recharge occurs by infiltration, ti or interception ti of the aquifer by rivers and streams Groundwater recharge is affected by precipitation, it ti actual evapotranspiration, topography, land use, soil type, land cover, aquifer transmissivity, vegetation characteristics, and contributions along active stream channels Understand the effects of land use changes and land cover changes on recharge Changing surface cover also changes surface temperatures which affects ET

22 What Else We Know (IPCC) Eleven of the twelve years from rank among the twelve warmest years in the instrumental t record of global l temperature data (since 1850). The 100 year linear trend of global surface temperature (from ) indicates an increase of o C Average Northern Hemisphere temperatures during the second half of the 20 th century were very likely higher than during any other 50 year period in the last 500 years and likely the highest in at least the past 1300 years. Gl b l l lh i i / Global average sea level has risen since 1993 at mm/year, with contributions from thermal expansion, melting glaciers and ice caps, and the polar ice sheets

23 We have changed the landscape in Florida and are affecting the climate, leading to LESS RECHARGE due in part to

24 Wetland loss: development, agriculture (changes in land use/cover) Less rain: changes in landuse/cover, climate change More heat: changes in landuse/cover, climate change Faster runoff: changes in landuse/cover, climate change

25 What else are we afraid of: Temperature increase = sea level rise Observations indicate this is ongoing

26 Potential Climate Change Problem

27 NASA projection of Florida over the next 100 years Note the Everglades is gone

28 Groundwater recharge will most likely decrease in many areas and depends on Current and historical land use sometimes having an effect from great distances Imperviousness of the surface Potential for stream interception of groundwater supplies (generally as a function of agriculture) Runoff patterns that may decrease retention, and thus percolation time

29 The scenarios that appear to have the most traction indicate the wet season will be wetter, the dry season drier, temperatures generally warmer but with more variation

30 Sea level rise: Additional Impacts: Increased hydraulic pressure from the ocean will threaten easterly wells with saltwater intrusion Aquifer contamination i due to inland penetration of sea water via canal system (salinity barriers are too far inland) Migration of saltwater up the everglades watershed could contaminate the headwaters of the Biscayne Aquifer A rising water table would inhibit storm water drainage threatening the water supply and habitability

31 Tropical weather: the extent, frequency, and intensity may increase If sea level is higher storm surge flooding will more frequent/severe Rain event flooding may be more severe due to a compromised stormwater drainage BUT: Hurricane Andrew in 1992 did not cause a significant or lasting effect on the aquifer

32 If precipitation and its patterns are changing, And the degree of natural groundwater recharge is changing And the population is growing We are not doing a lot of local research into groundwater recharge we tend to try to extrapolate from themodeling of scenarios in otherregions butregions there are almost no real world analogues to Florida and particularly South Florida How much water will be available to the inhabitants of South Florida and with what degree of reliability?

33 Other Issue Criticality Three other critical issues regarding climate change: how increasing hydrologic variability may affect total water supply and demand how energy usage, to treat / deliver potable water and to treat / dispose of wastewater, may contribute to climate change or variability, and in coastal areas how sea level rise may really impact all water supplies

34 What to do? Protect infrastructure from the impacts of climate changes Adapt to the changes Retreat from the change (worst case?)

35 Options to Protect t Water conservation short term, delaying Stormwater improvements Beach re nourishment efforts Protection of wetlands Protection of other high recharge areas Protection of sanitary sewer systems Altering wastewater disposal patterns to include beneficial reuse and salinity barriers Create protected reservoirs to capture water runoff to tide, such as the L8 reservoir

36 Relocation of wells Options to Adapt Water capture technology including horizontal wells Regionalization of water supply utilities Conversion to new water supplies such as desalination/reuse/asr Coastal armoring including lock and salinity structures Artificial recharge scenarios Transfer of resources between regions Diversion of stormwater to infiltration galleries

37 Options to Retreat t Extensive diking (the New Orleans scenario) and seawalls can the entire coastline continue to exist below sealevel???? Limit it development tin flood prone areas Relocation of large populations toward the central part of the state, which already faces water supply limitations

38 Recharge for Florida Reverse Osmosis Ultraviolet Advanced Oxidation HUGE CARBON FOOTPRINT Means $$$$$$$$$$$$$$$$$

39 New Direction Florida has gone from ASR to Floridan aquifer supplies to reuse with no real next option No new water has been added to the Everglades which was an original goal of CERP. If reuse is the answer, 500 MGD of wasterwater are created that need treating to reuse quality. An option is to build regional recharge facilities that treat secondary wastewater.

40 Construct piping pp to pump pto regional facilities consisting of filtration,cartridge filtration, UV disinfection, RO, and advanced oxidation. Use existing canals to discharge to the feeder canals and recharge the surficial system. If big issues could be overcome, water could be discharged into theeverglades Everglades adding adding thenew water it is not getting and additionally recharging thebiscayne aquifer

41 Far reaching reaching despite the costs Centralization of facilities would lower the costs of operation and construction Reduction and potential elimination of ocean outfalls Rd Reduction in the number of injection i wells Improved ecosystem conditions Improved efficiency in the utilization and retention of local and regional resources

42 Florida 2030 Vision All of Florida s water supply needs will be addressed by planning new infrastructure which can be adapted to future climatic impacts not the current situation the planning extends approximately 20 yrs developing supplies which h can be implemented in light of changing conditions Implementing policy initiatives iti to address climate change potential Keep an eye on the 2100 vision!

43 Pathway to Florida 2030 Visioni Risk assessments must be done to understand the uncertainties associated with the effects of climate change There must be a diversified approach to water supplies to minimize future risks associated with climate change There must be increasing conjunctive use of water supplies and an increased ability to transfer water betweenregions Water and wastewater infrastructure must be adapted to address sea level rise

44 Issues for Consideration Address climate impacts on drinking water and wastewater treatment facilities. Evaluate the borrowing capacity of utilities to fund infrastructure needs in the long term. In addition, develop/provide: Additional funding to harden existing drinking water andwastewater infrastructure, Incentives to reinvest in water capture technology (i.e.: horizontal wells and lock/salinity structures). Support research to develop Florida specific ifi climate change models in order to foster a sustainability/vulnerability y analysis handbook on climate change impacts

45 Issues for Consideration Provide assistance to smaller utilities in characterizing their current water supplies and how these supplies could be affected by climate change most water utilities are independent entities Provide direction to the water management districts on long term issues with protecting existing water supplies (including potential changes in state water policy) Develop and promote changes to state water policy to facilitate conjunctive uses of water sources, additional storage capacity to capture run off to tide and to promote regional sharing of water sources where needed

46 Solutions will depend on: Reductions in reliance on groundwater Structural improvements to improve recharge Conjunctive use of water supplies including wastewater for lesser quality needs

47 Requirements to really make anything change? Political will Major changes in water supply regulation, and groundwater rights usage Major expenditures of tax dollars

48 Questions?