Climate

Arid, Sub-tropicalRainfall (100-200 mm) is mainly during the summer in Sindh and in winter in BalochistanRelative summer humidity is 75%

Moderate temperature

The rocks are of marine origin and consist of limestone and clayLandmass is furrowed into many coastal islands of sizes ranging from a few hundred hectares thousands of hectaresThe islands are separated by many creeks

Soil comprises of river-borne clay, silt and sometimes loam. The soil rich in salts (sodium chloride, sodium carbonate and nitrates) is hard. The muddy soil (clay) is poor in other mineral substances.

River water supply

A regular supply of river water is necessary for the survival of the mangroves. The Indus and its tributaries flow 120 km to the south east of Karachi, however evidence suggests that previously it used to flow near Karachi.

Construction of irrigation dams on the Indus has decreased the extent and duration of the flow of the water. Earlier, before the dams, fresh water used to flow into the delta during low tides all year round.

Wind

VariableFaster during the summer (from 7.5 to 20.5 km/hr.High winds develop during the monsoon (June to September) resulting in rain and high waves sweeping over the delta

Cyclones, although not a regular occurrence, can hit the area during the monsoon