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Wilpattu National Park Villu hydrogeology: freshwater lenses and sand basin filtration?

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A
Arjun Forest•930 rep

What geological processes form the circular, rain-fed natural sand basins (Villus) that sustain wildlife in Wilpattu without perennial river inflows?

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The unique landscape of Wilpattu ("Land of Lakes") is defined by over 50 natural circular depressions called Villus. Geologically, they represent shallow karst sinkholes formed in underlying Miocene limestone beds overlain by deep Pleistocene red earth and coastal sands. Rainwater percolating through surrounding porous sand rims feeds an unconfined freshwater lens that floats above deeper saline groundwater. Because there are no surface inlet or outlet rivers, the sand rims act as natural geological filters, maintaining crystal-clear water bodies that persist through severe dry seasons.

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Dr Bandara DWC•1890 rep

Peripheral salinity varies dramatically between basins: Kokkare Villu contains saline water supporting salt-tolerant sedges, while nearby Kumbuk Wila remains pure fresh water.

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Arjun Forest•930 rep

Subterranean hydrological drainage connects adjacent villus through porous calcrete aquifers, equalizing regional water tables after monsoons.

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Dr Bandula GSMB•1850 rep

Mugger crocodiles (Crocodylus palustris) excavate deep muddy burrows into the banks of drying villus to estivate during peak dry seasons.

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Prof Gamhewage Bio•1950 rep

Safari vehicles must park strictly along designated perimeter viewing zones to prevent vehicle weight from compacting fragile sand rims.

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Sarah Field Scout•1720 rep

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