Hydro litho

• Groundwater lies beneath the ground surface, filling pores in sediments and sedimentary rocks and fractures in other rock types, representing 0.6% of the hydrosphere, resupplied by slow infiltration of precipitation (recharge), generally cleaner than surface water, accessed by wells.
• Groundwater is part of the hydrological cycle, with water moving from the surface to the ground and back again.
• Soil Exchanger
• Na + Cl - Reflects from the cation exchange process.
• From Seawater Sediment (Aquifer’s Matrix)
• Na + ½Ca – X 2 → Na – X + ½Ca – X 2
• Na + + ½Ca – X 2 → Na – X + ½Ca – X 2
• Porosity is the percentage of rock or sediment that consists of voids or openings, measurement of a rock’s ability to hold water, loose sand has ~30-50% porosity, compacted sandstone may have only 10-20% porosity.
• Permeability is the capacity of a rock to transmit fluid through pores and fractures, interconnectedness of pore spaces, most sandstones and conglomerates are porous and permeable, granites, schists, unfractured limestones are impermeable.
• The pore space of an aquifer is the spaces or voids between the solid material, the porosity of the aquifer is the volume of void space to the total volume, typically expressed as a percentage.
• Porosity is highly dependent upon the arrangement, shape, and size of the material, but the diameter of the grain size does not affect porosity, since it is the ratio of open space volume to total volume.
• The arrangement of various grains is called the degree of sorting and is illustrated below, well-sorted samples typically have higher porosity than poorly sorted samples, poorly sorted samples contain grains that tend to fill in the void spaces.
• Angularity can also affect porosity.
• Contaminant concentrations in the unsaturated zone may be present in four physical states: gas, sorbed to soil materials, dissolved in water, or immiscible liquid.
• An aquifer is a geologic unit that can store and transmit water at rates fast enough to supply reasonable amounts to wells.
• Samples with angular grains tend to have lower porosity than well rounded grains, especially of similar sizes.
• Porosity is the ease in which water flows through the rock's pore structure.
• Groundwater supports streamflow in between rain events (baseflow).
• The relationship between infiltration and surface runoff is rainfall - runoff = infiltration.
• A confined aquifer is an aquifer that has a confining unit (low conductivity) as an upper bound and lower bound.
• A rock may be highly porous, but if the pore spaces are not connected, it is not permeable.
• An unconfined aquifer is an aquifer that has the ground surface as an upper bound.
• Unconfined aquifers interact with surface water streams (i.e., groundwater surface water interactions).
• Unconfined Aquifer – water is in contact with atmospheric pressure – drill and well hit the water table.
• Unconfined Aquifer – Has a water table, and is only partly filled with water – Rapidly recharged by precipitation infiltrating down to the saturated zone.
• The following diagram represents hypothetical flow paths through a porous media.
• Infiltration (and runoff) is controlled by soil type, thickness, original water content, and precipitation characteristics.
• The porosity of rocks and unconsolidated sediments vary from 0.05 - 0.50.
• An aquitard is a rock/sediment that retards ground water flow due to low porosity and/or permeability.
• The transition zone thickness depends on both natural conditions such as permeability of the geological formation, tidal and recharge fluctuations and other factors such as artificial influences such as man-induced.
• The water table can be lowered by pumping, a process known as drawdown.
• The driving force of seawater intrusion into the aquifer is due to excess pumpage, which lowers the freshwater table, changing the direction and magnitude of groundwater gradients.
• Lack of fresh water presents a global problem of huge dimensions and a major effort is required to ensure good quality drinking water for the world population.
• Seawater can contaminate a freshwater aquifer through several pathways, including lateral intrusion from the ocean, by upward intrusion from deeper, more saline zones of groundwater system, and by downward intrusion from coastal waters.
• Energy gradients caused by water pressure and gravity also control groundwater movement.
• Saltwater has a higher mineral content than freshwater, making it denser and having a higher water pressure.
• Access to clean freshwater will be one of the biggest global resource problems of the coming decades.
• Groundwater usage has drastically increased over the last decade due to the rapid increase in visitors to the island.
• The top of the saturated zone is the water table.
• Manukan island is an ideal location for studying hydrochemical changes due to seawater intrusion due to the factors of it having been affected by seawater intrusion for many years and deteriorating due to the increase of human activities on the island.