• Water Resources Development Master Plan, Jamaica, Ministry of Agriculture, 1985.
• Report on the Geology of the Essex Valley Region, St. Elizabeth, Jamaica. Edward Robinson. 1990.

• Essex Valley, situated between the Spur Tree uplands and Santa Cruz mountain;
• Upper Morass, swampy lowlands made of limestone covered by peat deposits, acting as a discharge area for the Essex Valley ground water system;
• Lower Morass, an area of down-faulted, poorly karstified limestone, overlain by a relatively thin clay and peat sequence;
• Pedro Plains, a limestone aquifer situated between the coast and the Santa Cruz mountain;
• South Coast Basin, which is a series of east-west ridges descending to the coast in the south-eastern part of the basin.
• Nassau Valley, a small unit north of the Upper Morass, being separated from it by the Nassau Mountain.

Because the entire basin is underlain by limestone (Newport Formation of the White Limestone Group), surface drainage is found only in the Upper Morass to the north, where a series of springs feed the tributaries of the Black River system. (A small river occurs in the southeast of the basin, flowing from springs a short distance directly to the sea, as the Alligator Pond River.)

All other drainage is subsurface.

The Essex Valley is the most important region in the basin considering extensive ground water development for two competing users: bauxite industry and domestic water supply. As a "by-product" of the bauxite-to-alumina processing waste ponds are created. Due to karstic nature of the rocks underlying the ponds, the industrial effluent stored in such ponds finds its way down to the limestone aquifer.

In 1990, Professor Robinson, now with the University of the West Indies, carried out a geological mapping of the Essex Valley region around the ALPART mudlakes (equivalent expression to waste ponds). Executive Summary of his report is hereby completely reproduced, with minor editing, with his permission.

• The only rock unit involved with the ground water system of the region is the upper part of Newport Formation, a unit of the White Limestone Group. The base of this unit lies at a depth of more than 4,500 ft (shown is an oil exploration well at Santa Cruz) below the sites of the mudlakes, below the water table, and below the saltwater interface below the freshwater lens.
• The lithology of the Newport Formation is mainly soft, friable, even chalky and rubbly limestone, with some primary intergranular porosity, case-hardened at the surface to produce limestones without primary permeability.
• The limestones have been extensively fractured, ranging from major faults to minor faults and joints, so that the development of extensive secondary permeability is to be expected.
• There is a major fault system, here called the Essex Valley System, which passes through both lakes and extends northwards as far as the Upper Morass, just east of Santa Cruz, and southwards to intersect the faults of the South Coast Fault System. This has the potential to provide preferential conduit type flow both northwards and southwards from the mudlakes region.
• Secondary faults cutting this main set at right angles appear to be of slightly later age. They provide potential paths for conduit flow laterally in NE or SW directions, but are not as extensive as the main system. However, some of these may provide flow paths for ground water, as at the Alpart Pepper well field.
• The presence of extensive, even pervasive minor fracturing of the limestones, with a strongly preferred NE-SW orientation has the potential for providing additional directional flow paths for the ground water system, NE and/or SW.
• The ridge of the Santa Cruz Mountains to the southwest of the study area (The Essex Valley) would probably coincide with a water table elevation that is higher than water table near the mudlakes, inhibiting so the flow in the direction of the Santa Cruz Mountains.

• As conduit-type flow (through wide joints and cave systems) north and south along the Essex Valley Fault System, with branching lateral flow to the northeast where secondary faults intersect the main system;
• As more diffuse, but still directionally controlled flow, from anywhere along the main Essex Valley Fault System, via minor fractures and joints, to the northeast.

• There is no pumping in the Essex Valley. This is a hypothetical case showing the direction of ground water flow under no-pumping conditions.
• The Santa Cruz Mountain (south-western limit of the model) is a no-flow-across line, being a divide between the western and eastern flanks of the mountain.
• The coast line is the constant head line with H=0 m. This is to say that the ground water would finally outflow into the sea.
• The eastern boundary of the flow domain is the Spur Tree Hill, or the Manchester Uplands. Again, this line is a no-flow-across line.

Hydrogeologically, such a flow pattern points at the flow path of an eventual contaminant damped into mudlakes. Mudlakes being almost at water divide, would let the contaminant flow in both north and south directions. This is in accordance with the conclusions of the geological mapping report by Professor Robinson.