Groundwater Basics
Speaker - Greg Cherry, Geohydrologist/Hydrogeologist, USGS - PR

Locating Dams on St. Croix:
Speaker - Rudy O'Reilly, Soil Conservation Service, USDA

Virgin Islands Data Atlas Series
Speakers - Nick Drayton, Director of Conservation Programs and Barry Devine, Chief Scientist Conservation Data Center, UVI, Eastern Caribbean Center

These are areas of unique, scarce, or fragile natural habitats or physical features; areas of high natural productivity; or essential habitat for living resources or endangered species, including fish and wildlife and various levels of the food chain critical to their survival. Examples of the SNA's are unique or remnant plant and animal species of special interest; natural areas that provide scientific and educational value; and areas necessary for wildlife for the nesting, spawning, rearing of young, or resting during migration. Also included are areas needed for the protection, maintenance, or replenishment of coastal lands and resources.

Culturally Important Areas
These are coastal lands and waters where sites of historic and archeological significance, cultural or traditional value, or scenic importance are located.

Recreational Areas
These include lands and waters of substantial recreational value and/or opportunity. Examples include areas suited for public parks, beaches, boat launching and mooring, and other recreational activities.

Prime Industrial and Commercial Areas
This designation reflects coastal lands and water with existing or potential geologic, topographic, and infrastructural conditions amenable to industrial and commercial development, especially those requiring a waterfront location.

Developed Areas
These are urbanized or highly populated and intensively developed areas, where shoreline utilization and water uses are highly competitive or are in conflict.

Hazard Areas
These include coastal locations that, if developed, would pose hazards because of periodic flooding, storms, erosion, or land settlement.

Mineral Resource
These are coastal areas with existing or potentially important mineral resources, particularly sand deposits for commercial extraction.

AREAS OF PARTICULAR CONCERN (APC)

DEFINITION: The Virgin Islands Coastal Zone Management Act of 1978 stipulates that certain areas of our islands are of greater significance, whether for economic, cultural, or environmental reasons, and are nominated as Areas of Particular Concern (APC's). As part of the Coastal Zone Management Program (CZM), the VI government has developed the criteria for areas that are nominated as being of particular concern.

CLICK ON THE APC AREA ON THE MAP FOR MORE INFORMATION

AREAS OF PARTICULAR CONCERN ON ST. CROIX
On St. Croix, nine areas on the island have been designated APC's. They appear in order from east moving west, not in a prioritized order, for actions to be taken.

1. Christiansted Waterfront

a) Fort Christiansvaern west to the new site of Seaborn Aviation and the operation of their seaplanes (west ramp).

Water quality in Christiansted Harbor has been degraded by numerous dredging activities, urban runoff, and sewage and oil discharges. A well-developed fringing reef system which defines the harbor, has been, and continues to be, under severe stress. Untreated sewage discharges continue despite the completion of the Christiansted interceptor system. Untreated wastes are discharged into the harbor by individuals on live-aboard vessels.

b) Fort Louise Augusta-Altoona Lagoon-Gallows Bay
Port Authority facilities at Gallows Bay handles a significant amount of maritime commerce of small inter-island freighters, local and visiting commercial fishing vessels and vessels under contract to the U.S. Navy. This area also contains Christiansted's only marina, St. Croix Marina, with dockside facilities for recreational, and military vessels up to 300 tons.

Altoona Lagoon is fringed by a well-developed mangrove system that provides important habitat for numerous birds, fish, shrimp and shellfish species. It is also the site of a heavily used public boat launch ramp and public beach.

2. Southgate Pond - Cheney Bay

Southgate Pond has been divided by fill to form two separate ponds. The western portion was opened to the sea and extensively modified by dredge and fill operations to create the 140 slip marina, Green Cay Marina. The eastern larger pond is fringed by a well-developed mangrove community and is an important wildlife habitat, scenic and educational area. This area serves as the nesting grounds for three species of federally endangered sea turtles. Southgate Pond and Cheney Bay Beach are recommended to be included in a Territorial Park System.

3. St. Croix Coral Reef System

The best example of coral reefs in the U.S. Virgin Islands is found offshore of St. Croix. These reefs are areas of high marine productivity, supporting the traditional reef fish/lobster fisheries, and provide spectacular opportunities for underwater recreation. The bank-barrier reefs, which extend along the entire northeastern and southeastern coasts, are the most extensive and developed of all the St. Croix reefs and, as such, deserve special management. The coral reef APC extends from Long Reef off Christiansted Harbor eastward to include the nonfederal areas of Buck Island reef, Coakley Bay-Teague Bay-Boiler Bay reefs to East Point and the southeastern reefs from East point to the west end of the Great Pond Bay. Also are included the well-developed algal ridges off the southeast shore and the deep reefs between Cane and Davis Bays.

4. East End

This area includes the northeast coast from Cramer Park to Point Udall, the easternmost point of the VI, then westward along the southeast coast to include Jack and Isaacs Bays. Located in this vicinity is the National Radio Astronomy Observatory's radio wave telescope facility. The ecology of the eastern end of the island, because of its dryness, steep slopes, soil type and proximity to wind and salt spray from the sea, is extremely sensitive to disruption. Water quality in Jack and Isaacs Bay beaches is considered pristine. The well-developed fringing coral reef systems offshore make this area one of the best snorkeling sites in the VI. Two federally endangered species of sea turtles nest on these beaches. In fact, Jack Bay beach has been recorded as the most important hawksbill turtle nesting beach in the USVI. Jack and Isaacs Bays are recommended to be included in a Territorial Park System.

5. Great Salt Pond and Bay

Great Salt pond is the second largest salt pond in the VI, with black mangroves fringing most of the Pond. In addition to serving as a large sediment trap between upland areas and Great Pond Bay, Great Pond is a significant wildlife area and the most important bird habitat on St. Croix. The bank-barrier reef offshore affords protected back reef waters for extensive turtle grass meadows. The proximity and relationship of these three natural systems makes the Great Salt Pond and Bay a unique natural area. This area is recommended to be included in a Territorial Park System.

6. South Shore Industrial Area

The industrial area extends from Canegarden Bay to Manning's Bay, just south of the Henry E. Rholsen International Airport. The shoreline and adjacent inland areas are among the most heavily developed in the Virgin Islands. Massive dredge and fill activities have occurred throughout most of this area. Development includes:

a) HOVENSA, LLC
b) St. Croix Alumina
c) Virgin Islands Commercial Port Facilities
d) Virgin Islands Port Authority Container Port
e) Virgin Islands Port Authority/Krause Lagoon Dock
f) St. Croix Landfill
g) Wastewater Treatment Plant
h) Randall "Doc" James Racetrack
i) Texaco Storage Facility
j) Virgin Islands Rum Industries

There are numerous potential adverse environmental impacts associated with the entire Southshore Industrial Area. The foremost concern is for large scale oil spills. Other adverse impacts include degradation of water quality, which results from the massive alteration of drainage patterns, both in the immediate area of development and also runoff problems associated with upland development. Another concern is that of waste discharge in the forms of chemical and thermal wastes from industrial plants, the sewage treatment plant and the solid wastes disposal site.

7. Sandy Point

Sandy Point is a peninsula of approximately 500 acres at the southwestern tip of St. Croix and has been designated a National Wildlife Refuge since 1984. Within Sandy Point are located the largest salt pond in the VI and the longest stretch of beaches in the VI. The beaches are very popular recreational areas and nesting sites for three species of federally endangered sea turtles.

8. Frederiksted

The Frederiksted Pier is an important commercial port for cruise ships, military vessels and other commercial vessels. Much of the town is included in the Historic District. Unfortunately, severe damage to the coral reef ecosystems has occurred off Frederiksted due to large commercial and military vessels anchoring offshore.

9. Salt River - Sugar Bay - Triton Bay

Salt River is one of the few major mangrove lagoons remaining in the USVI. It is the largest on St. Croix, containing 45 acres of white and black mangroves along the shoreline. The fringing red mangrove prop roots provide critical habitat for juvenile reef fish species. The mangrove forests are critical habitats for winter migrating birds and numerous endangered species.

Salt River is of major historical and archeological significance. In 1965, the VI government established a five acre Territorial Park in the area which includes the first and best documented site of Columbus's second voyage to the Caribbean in 1493, Cape of Arrows (Cabo de las Flechas), the site of the first violent encounter with West Indians, and aboriginal artifacts and remains dating from 350 AD including a prehistoric village, ball court, and a 16th century fort. Salt River, Sugar Bay, and Triton Bay are recommended to be included in a Territorial Park System.

Groundwater is the primary source for new development on St. Croix as well as all other communities. The future of water management on St. Croix requires a complete understanding of water cycle dynamics and the water budget. This is all essential information needed for proper land use planning. There are new technologies to aid in water resource analysis. One tool used to increase our understanding of these dynamics is GIS. Global Information Systems (GIS) link geographical features to a data base containing information about that particular geographic feature. For example, on our island of St. Croix the Great Pond mangroves can be monitored. Annual or seasonal changes in the number of acres the salt pond encompasses can be determined for trends and patterns by analyzing GIS maps. The GIS database can also answer questions about ground cover by analyzing reflective properties of the surfaces. In this way, grasslands can be distinguished from shrubs, trees, and other vegetation. The commercial applications are extensive. For example, if an investor wants to construct a hotel at a given location, by analyzing the GIS the investor would be able to glean information on beach type, restrictions, and significant environmental data. Land use planning can utilize GIS to determine the environmental consequences and advantages of decisions made in reference to zoning laws. The USVI Development Plan provides a frame work for proper management of water and land resources. It was published in June 1994 in a collaborative effort involving the following agencies:

Department of Planning and Natural Resources Community Advisory Committee Coastal Zone Management Commission Department of Public Works VI Housing Finance Authority Police Department Fire Services

Water and Power Authority Department of Economic Development and Agriculture VI Port Authority Department of Education Department of Housing, Parts and Recreation Department of Property and Procurement

The Land Use Plan classifies St. Croix into Intensity Districts. This map is a visualization depicting a broad simplification of some of the Intensity Districts proposed in the USVI Development Plan. A brief explanation of these areas and some of the recommendations that have been proposed are described. Examples of appropriate land uses are also listed. The information can be accessed by clicking on the links to the right.

A Agriculture (District 1) R1 Residential Low Density (District 2) R2 Residential and Moderate Commercial Activity (District 3) U Urban (District 5) I Industrial (District 6) Waterfront Intensity Districts

This map was created by the United States Geological System (USGS) and shows the number of gallons per minute that can be obtained from wells in these locations. The yellow represents between 5 and 100 gallons per minute in the alluvial aquifer. Alluvial and beach deposits are sand-size sediments. The blue represents areas where very solid, impermeable rock is under the surface of the ground, keeping the groundwater closer to the surface. Generally, the yield of water from wells is greater toward the south central part of St. Croix. The red symbols give examples of some of the intensity districts proposed in the Land Use and Development Plan.

R1-Residential Low Density (District 2) Residential neighborhoods and parks coexisting with small scale crop farming in these areas not typically served by potable water and sewer lines. This district is located primarily in sparsely developed and undeveloped areas. It is intended to accommodate active and passive recreational facilities and neighborhood-oriented commercial activities. Return to the Intensity Map Top of the Page Click on the photo to show an enlarged version, close the window to return to this page.
The watershed is the total surface area from which water passes over on its way back into the ocean. Locally, there are 47 different watersheds. The VI Government leases one-acre plots to farmers in this area. Water is trucked to the sites from the adjacent Department of Agriculture	A simple, gravity fed system could be built to efficiently deliver irrigation water to the farmers of the Community Gardens. The tree farm above is one of the many uses appropriate to this area. Aquaculture and horticulture once thrived here.
This plot is about 1/4 acre and is irrigated by a hose attached to a pump from a free standing cistern. This is tania, a root crop and a main dietary staple of the indigenous peoples of Pre-Columbian times.	Small sheep farms exist in the midst of low density neighborhoods. Ball parks, playgrounds, and churches are also permitted in this district.
Restoration and better management of riparian buffers (vegetation growing along guts, creeks, and ponds) can reduce the effects of non-point source pollution. The guts from these hills can be restored to reduce runoff.	Homes in this district typically are not served by potable water and sewage lines. Most homes have cisterns. The windmill above is pumping water into a trough that cattle access as their primary source of drinking water.

Speaker - Greg Cherry, Geohydrologist/Hydrogeologist, USGS - PR
gcherry@usgs.gov
749-4346 x 230
http://pr.water.usgs.gov

Reported by Kate Baker

Greg Cherry worked for many years on St. Croix, studying and evaluating many of the parameters of St. Croix’s groundwater.

Groundwater occurs almost everywhere. It is recharged from precipitation - about 3% of precipitation actually goes into the aquifer. Water has to get below 6 - 10 feet to get into aquifer.

An unconfined aquifer is one in which the water table system is open to the atmosphere. Drawdown is the depletion of an unconfined aquifer by a well or wells. A confined aquifer contains a layer of impermeable material above aquifer. The aquifer is under pressure from the confining layer. A well over a confined aquifer becomes a release point; the water is pushed up to the surface by the pressure of the layer.

Another important quality in an aquifer is the characteristic the USGS calls Hydraulic Head, which is the distance from water level to sea level - this is the quality they believe actually runs the aquifer.

Transmissivity of an aquifer is the measure of how fast water can travel in an aquifer. Most aquifers move between 250 - 1000 square feet of water per day. St. Croix is a very slow aquifer, in general moving less than 250 square feet per day.

The sustainability and depletion of an aquifer system are important issues the USGS investigates and evaluates. For example the depletion of the aquifer in the central U.S. has led to “water wars”, as communities and farmers compete for the water. Aquifer depletion leads to soil compaction, as the soil takes up the spaces previously occupied by water. This compaction can be enormous - HUNDREDS of feet.

Runoff (water that does not enter an aquifer, but instead washes into a low-lying body of water) becomes an important consideration. Construction must be evaluated, because urban runoff is usually about 75% of any rainfall, compared to the water that runs off in a forest, usually about 30% of precipitation.

One important part of the USGS work in a region is to calculate a Groundwater Budget for that region. The simplest equation for this budget is: recharge (water entering aquifer) = discharge (water leaving the aquifer). A simple example is the Long Island Budget Analysis:

•Recharge
Precipitation = 2475 cubic feet per second

•Discharge (cubic feet per second)

Evapotranspiration	1175
Groundwater discharge to sea	725
Stream flow discharge to sea	525
Evapotranspiration from groundwater	25
Spring flow	25
Total	2475

The USGS utilizes a systems approach to water management, where the groundwater system and wetlands system are evaluated together, and seen as a single system.

Publications used*:

Sustainability of Ground Water Resources

Ground Water Atlas of United States, Segment 13, Alaska, Hawaii, Puerto Rico, Virgin Islands

Storm-Tide Elevations Caused by Hurricane Marilyn

Fact Sheets on Kingshill Aquifer

Aquifers of the Caribbean Islands

Atlas of Groundwater Resources in Puerto Rico and the US Virgin Islands

*Available through USGS website or
USGS
Earth Science Information Center
Open File Reports Section MS 517
Box 25286, Denver Federal Center
Denver CO 80225

There are several criteria in selecting a site and placing a pond on St. Croix. These are soil considerations, the type of pond needed, the proposed use of the pond and the aquifer where the pond will be located.

The soil on St. Croix is not conducive to ponds. The most common St. Croix soil is Victory (19% of all VI soil) and is usually 4 - 8 inches deep. Before a pond can be located, it is important to determine soil runoff on annual basis for that area, to make sure that the pond will not result in increased nonpoint source pollution. Most ponds are not connected to guts and are basically catchments for water. It is important to survey to identify lowest point on land - the best place to locate the pond. A survey will also determine where overflow water will exit, which will be the primary (or principal) spillway for the pond. It is important to locate an emergency spillway to be used during flooding to divert water.

The type of pond depends on water needed. The most common type on St. Croix is an excavation pond, where you just dig and let water fill. A berm pond, in which you build up soil around water with rocks and clay. (A berm is just a wall of rock or clay) A dam is really just a concrete berm. The most famous dam on St. Croix, Creque Dam has one concrete side and soil berms on others. Some other dams on St. Croix are in Bethlehem, Fountain Valley and Mon Bijou at Windsor Farm. Most are built by USDA. Creque Dam was built by the Army Corps of Engineers. One berm pond, easy to find, is in Estate Whim, right beside the highway, just before Johnson's Road, by the Australian pines.

There are a variety of uses for ponds on St. Croix, but the largest use is actually to recharge the aquifer, not feeding livestock as many people assume. A pond that recharges the aquifer keeps salt water out of the aquifer, which would poison the water source of the farmer. The second largest use is for irrigation of crops.

The Soil Conservation Service and the USDA use the Unified Water Assessment to evaluate pond locations. Their goal is to prevent nonpoint source pollution from these ponds. Some of the strategies provided to pond-builders include: riparian buffers (tiered vegetation on berms to prevent erosion), assisting the farmer to cut back and enforce stock grates, and the proper number of livestock in an area to safely use the water. The guideline they use is 3 acres per 1 animal unit where 1 animal unit = 1 bull or 1 cow and calf.

While agriculture is a neglected source of livelihood on St. Croix, it is important to conserve the resources we do have, and not have the detrimental nonpoint source pollution found in the United States in agricultural regions. Careful pond and dam construction is an important part of our conservation efforts.

Virgin Islands Data Atlas Series

Nature Conservancy
Nick Drayton, Director of Conservation Programs
#52 Estate Little Princess
PO Box 1066
Christiansted VI 00821
ndrayton@islands.vi
(340) 773 - 5575

Conservation Data Center, UVI, Eastern Caribbean Center
Barry Devine, Chief Scientist
2 John Brewer’s Bay
St. Thomas, VI 00802-9990
bdevine@uvi.edu
693-1038

Reported by Kate Baker

Presenting together, Mr. Drayton and Dr. Devine represented the Conservation Data Center, whose mandate is threefold:

•Rapid Ecological Assessment - develop a method for builders, developers, and conservation groups to quickly evaluate the effects of development on a specific Virgin Island region.

•Marine Systems Documentation - to consider the Virgin Islands from “reef to ridge”, or to express the connection between watersheds and reefs. One stumbling block to this documentation was the unique classification system required in the VI. It is usually done by species dominance. However, this was not possible in the VI because in general, no individual species dominates a habitat type.

•Development of a Conservation Plan - to document species (both plant and animal) that are unusual or uncommon. This was essential because the Caribbean has been identified as #7 worldwide region “hot spot”. This species loss is due to loss of habitat diversity, exotics (plant and animals brought in that compete negatively with native species) and habitat fragmentation (isolation of habitats that results in species extinction). A conservation plan is also essential to identify ecotourism areas, another facet of the work at CDC.

The mandate is being met by producing data-rich maps of the Virgin Islands. This has been done using GIS - Geographic Information Systems, or computer mapping. These maps incorporate National Vegetation Classification Systems and consistent worldwide descriptions of vegetation. The Caribbean has its own system, the Caribbean Mapping Project, which is an adaptation of the Federal classification system based on community structure. Some of the St. Croix categories are:

•Moist Forest (St. Croix has less than 1% of moist forest)
•Dry Forest
•Woodlands
•Shrublands
•Pasture
•Wetlands
•Developed

The software used by the CDC is Arc View or Arc Explorer. This software enables a user to combine data sets to produce a map that meets the particular needs of each user. The CDC offers courses in using the software, data sets, and maps.