ARTIFICIAL PONDS IN THE CAYMAN ISLANDS
GUIDELINES TO MAXIMIZING WILDLIFE VALUE AND MINIMIZING WATER QUALITY ISSUES
INTRODUCTION
Due to the low-lying nature of land in the Cayman Islands new developments often encounter and
impact natural wetland areas. Some developments deliberately engineer artificial ponds and pools to
excavate fill and raise the level of surrounding areas. Natural freshwater pools are a rare habitat in the
islands and one which has been much eroded by development in recent years. To these ends, if properly
constructed, the creation of artificial wildlife ponds has the potential to generate valuable areas for
wildlife. Unfortunately, in the past, poor planning of artificial pools has meant that far from providing
new habitat, badly thought-out excavations have resulted in areas unusable by most wildlife.
Additionally, poorly designed ponds have caused serious water quality issues. This has given rise to the
death of wildlife and unpleasant conditions for people living close by.
The Department of Environment has produced this simple list of guidelines for the construction of ponds
with the objective of maximizing the value of artificial ponds for wildlife and minimizing the water
quality issues associated with inappropriate designs.
1 - PLANNING YOUR POND
1.1 – HEALTH AND SAFETY
Ponds can present a potential hazard to young children. Dangers can be minimized by ensuring that
ponds are appropriately sited within a development and access is suitably restricted through fencing,
gating and landscaping design.
1.2 - STORM WATER MANAGEMENT
Provision of ponds and pools, both natural and manmade, can form part of an effective storm water
management strategy for your development. Equally, the filling of natural ponds and blocking of natural
water courses can result in flooding issues, both on site and off.
1.3 - LOCATION
Pick an appropriate site for your pond. While most locations are suitable for wildlife ponds, some are
better than others. If your land is in close proximity to an air strip, the birds attracted by freshwater
areas may present a bird strike hazard. Areas adjacent busy roadsides, power lines and floodlights are
also to be avoided where possible. Ponds should also be sited away from areas of nutrient enrichment,
e.g. septic tanks, if water quality issues are to be avoided. In all cases, working with the natural
environment will make for the best results – where possible, natural low-lying areas and pre-existing
native vegetation should be incorporated into your design.
1.4 – WATER LEVEL
The wildlife value and aesthetics of your pond will depend to a large extent on the water level it
maintains. To these ends, it is best to understand the depth of the water table and the dynamics of the
hydrology in your area prior to commencing excavations.
1.5 – EQUIPMENT
A bulldozer or scraper is best for constructing larger ponds and sculpting slopes and edges. A backhoe or
excavator may be required to work in deeper, wetter sections.
2 – DESIGNING YOUR POND
2.1 – THINGS TO AVOID
Excavations for fill are typically large, deep and steep-sided. Ponds of this nature are of little or no value
for wildlife. They can also represent a public health hazard and are most prone to water quality issues.
2.2 - SHAPE AND SIZE
Generally speaking, larger ponds (e.g. 2500 sq ft) have the potential to attract most wildlife if properly
designed.
Introduction of curves into your pond design will improve its aesthetic value, complementing and adding
value to associated developments. Ponds can be constructed in unusual shapes, to complement the
natural and built environment.
A mosaic of water areas interspersed with native landscaping will support the greatest possible variety
of wildlife. With appropriate design and landscaping, even the smallest ponds and scrapes can support a
significant number of species.
2.3 – MAXIMIZING VALUE FOR WILDLIFE
The key to maximizing the wildlife value of ponds is to incorporate as many different habitats into your
design as possible:
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ponds should be surrounded by a broad belt of vegetation – the wider the better, but should be
at least 30ft.
surrounding vegetation should be low in some areas (cut grass or, preferably, native ground
cover), incorporate reed beds (Typha) and water-tolerant native trees and shrubs (see 2.5).
Trees and shrubs can be used as cover by wildlife, shielding sensitive species from disturbance.
Vegetation can also be used to control access to the pond by people.
surrounding vegetation should overhang the pond wherever possible, providing shade and cover
over the water. This will contribute greatly to the pond’s biodiversity and also support better
water quality.
from the edges, ponds should shelve gently downward. The slope should be as gentle as
possible (10:1 or less).
pond edges should incorporate significant shallow areas – (0-1 ½ ft deep) - these areas function
as habitat for wading birds and are a practical health and safety measure. Ideally, such shallow
areas should constitute 25-40% of the pond area. Intermediate depth areas should vary from 1
½ -3 ft deep; constituting 25-40% of the pond area. Deeper areas should be 3-4 ft in depth;
constituting 25-40% of the pond area.
water depths greater than 6 feet have reduced value for wildlife, benefit less from wind-driven
aeration and circulation which helps to maintain well-oxygenated pond water and bottom
sediments, and become increasingly susceptible to water quality issues. Provision of some
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deeper areas will ensure the presence of water year round in the event of drought – annual
fluctuations in water level of 3-4ft can be expected in most places.
the base of the pond should be smooth and undulating - this encourages a mosaic of open water
and underwater vegetation to develop, which is attractive to waterfowl.
wildlife and aesthetic value can be further augmented by the provision of vegetated islands,
which will attract roosting and possibly nesting birds. In the absence of islands, tethered floating
platforms can be used as an alternative. Loose gravel islands may attract unusual species such as
Antillean Nighthawk and Least Tern.
FIGURE.1
Examples of a good basin design.
To the left, this plan view shows an irregular design, with the water
body interspersed with lines of vegetation. The slopes are shallow,
with depths illustrated with contours at 1ft intervals.
Above is a cross-section of the pond, demonstrating a shallow
slope and undulating basin design, with alternate areas of deeper
water, and shallow sections for aquatic plants.
2.4 – LANDSCAPING
The importance of landscaping to the aesthetic and wildlife value of ponds has been touched on in
previous sections. In all cases, attempts should be made to maintain any native vegetation already
present on site. The maintenance of mature, overhanging trees, which can shade the water, will greatly
add to the wildlife and aesthetic value of the pond. Shading of water also contributes to the
maintenance of good water quality. Landscaping with native trees will help attract native species to the
pond, particularly birdlife.
Exotic landscaping is costly and many introduce unwanted invasive species to a wildlife pond, however,
some exotic species can be added to bring some added colour or variety to a native landscaping scheme.
2.5 – WATER QUALITY
Poor water quality is an issue for wildlife as it brings with it a reduction in biodiversity.
Poor water quality is also an issue for residents living adjacent to ponds, bringing with it aesthetic issues,
including visually unappealing algal blooms and scum, foul odors and noxious fumes, fish kills and, in the
worst cases, water toxicity and health issues for people and pets.
Poor water quality arises from
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nutrient run-off: most commonly, the source is fertilizer runoff from landscaping and agricultural
land, washed into the pond during heavy rain. This can be avoided by reducing the amount of
fertilizer added to land nearby, by surrounding the pond with an appropriate buffer of
vegetation.
nutrient leaching: most commonly, the source of enriching leachates such as nitrogen and
phosphorus is sewage systems and deep wells. This can be avoided by siting your pond away
from deep wells and sewage systems.
nutrient loading: this may occur when people feed wildfowl or add fish to a pond, artificially
increasing its nutrient content. This can be avoided by allowing a pond to populate and
equilibrate naturally.
poor mixing of the water column: this usually arises from ponds being dug too deeply, and can
be exacerbated by the addition of nutrients, physical constrictions, and direct sunlight. Poor
mixing can be avoided by not digging ponds too deeply, and further mitigated by the addition of
water pumps and water features.
lack of oxygen: this usually arises when a pond does not possess enough oxygenating plant life.
Aquatic plants will not thrive if the water column is too deep, as they will not receive sufficient
sunlight. Algal blooms will also block out sunlight to oxygenating plants below and absorb
oxygen at night. This situation can be avoided by not digging your pond too deeply, and also by
maintaining elevated ridges within the pond which are able to support oxygenating vegetation.
ecological collapse: when water quality issues are extreme and persist, “ecological collapse” can
occur. Under such circumstances, the ecological structure of a pond can “flip” from supporting a
diverse natural complement of species, to a self-perpetuating species-poor slump. Such ponds
are characterized by dense algal blooms (e.g. “pea-soup” color) and fish kills, which respectively
further deoxygenate the water and add further nutrients, perpetuating the collapsed state of
the pond. Once in this state, the slump species maintain their own ecological balance,
preventing the pond from recovering. This makes active (and expensive) remedial action
necessary, (such as draining the pond and removal of dead fish), if the pond is to recover its
natural balance. Algal blooms can be monitored by using a “secchi disc”. In a healthy pond
secchi disc visibilities should not fall below 30-45 cm (12-18 inches), for details see
http://pdf.gaalliance.org/pdf/GAA-Boyd-Feb04.pdf. A secchi disc is easy to make, and can
provide a useful warning of impending algal blooms associated with low oxygen levels especially
at night.
For more information see http://myfwc.com/media/131494/Fish_Kills_in_South_Florida.pdf.
2.5 – NATIVE LANDSCAPING FOR PONDS
LARGER TREES
Royal Palm
Roystonea regia
Bitter Plum
Picrodendron
baccatum
Red Birch
Bursera simaruba
Mahogany
Swietenia mahagoni
Smokewood
Erythroxylum aureolatum
Pepper Cinnamon
Canella winterana
Fig
Ficus aurea
White Mangrove
Laguncularia racemosa
SMALLER TREES
Buttonwood
Conocarpus erectus
Cabbage Tree
Guapira discolor
Wild Cocoplum
Savia erythroxyloides
Mangrove vine
Rhabdadenia biflora
Bloody Head Raw Bones
Capparis flexuosa
Christmas bush
Allophylus cominia
SHRUBS AND FLOWERS
Swamp fern
Acrostichum sp.
Snow Berry
Chiococca alba
3 – FILLING YOUR POND
3.1 – WATER
Your pond should be dug to such a depth that it is filled for the majority of the year by virtue of the
natural water table.
If your pond dries out and you wish to replenish it, rainwater from a cistern or ground water from a well,
rather than tap water, will be the most beneficial.
If you wish to encourage introduction of natural pond life and native species to a newly dug pond, the
addition of a few buckets of water from a neighboring well-established pond will give your pond a head
start.
3.2 – AQUATIC PLANTS
If your pond is excavated into rock, adding an organic base (such as a thin layer of topsoil, perhaps 6
inches) to the excavated base will encourage the more rapid establishment of water plants. If you
provide an organic base, aquatic plants should naturally establish in due course (additional planting is
not necessary).
3.3 – FISH
Native species and non-native species do not generally mix well in ponds. It is often thought that adding
fish will help keep algae and greening of ponds down, but fish generally add to the nutrient loading of
ponds. Wildlife ponds for native species and ornamental ponds which feature exotic species (such as
goldfish, koi carp, and introduced waterfowl) are best kept separate. Tilapia should not be stocked
because of their potential to become a pest fish, capable of competing with native fish for food and
living space. DoE investigations since 1991 have shown Tilapia to be the species of fish most commonly
involved in fish-kill events in Grand Cayman.
3.4 – ATTRACTING BIRDS
With appropriate design and landscaping, your pond will naturally attract wild birds in time. Attracting
larger numbers of birds, particularly by feeding waterfowl at the edges of ponds, will introduce
additional nutrients to the pond. If your pond does not have the capacity to adapt to this elevation in
nutrient levels, water quality issues will quickly result. The feeding of waterfowl is a seemingly generous
act, however inappropriate feeding can have serious repercussions for waterfowl including nutrient
deficiencies such as “Angelwing”, resulting in deformity and even death. Feeding also encourages
unnatural behaviour, including delayed migration and aggressive behaviour towards people.
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These guidelines were adapted from the Excavated Ponds for Wildlife guidelines, developed by the Minnesota Department of Natural
Resources.