Water resources problems can be classified into 3 categories: Too much water, Too little water and water contamination. The problems like floods and droughts are natural events that are one of the water resource problem. These problems can also originate when the humans do not take right decision such as they build in areas that are in danger of flooding.
TOO MUCH WATER
Too much water represents the floods. Floods are caused when the rivers spilled over and surrounds the surrounding land. In ancient Egypt this happened an after floods a thin layer of sediments accumulated in soil that enriched the soils with nutrients. In ancient times property loss or life loss was not as much high as in today life.
Damage
Modern floods cause the widespread destruction in terms of property loss and loss of life. This is due to the humans who build their houses or buildings in the flood plain areas (areas that border a river and prone to floods). They remove the plantations from the areas that absorb the flood water and enriches the soil with nutrients. Hence the property and life loss occurs at higher rate. Floods are more destructive in nature as in US 9 out of 10 disasters are of floods.
Causes of Floods
As the forests on the mountains, hillsides are best absorbers of water coming from rainfall. When the forests are cut down the heavy rainfall causes the soil erosion and it make the lowlands at the risk of flooding.
The other reason is that humans remove the plantations from flood prone areas and made their buildings or roads. As paved roads and buildings cannot absorb the water so the water runoff to the sewers. These leads to flooding.
Measures to prevent Floods
To prevent the floods the levees are built near rivers but in floods expensive levees even fails. There should be a restrict ban to build on flood plain areas. In California January 1997 flood, 8 people were killed, more than 16,000 homes were damaged and more than $1.6 billion was damaged.
TOO LITTLE WATER
In Africa and Asia 40 % of population live in the arid or semi arid areas. They have to walk miles to carry water with them from rivers but that water is heavy water. Water shortage occurs due to overdrawing of surface water, aquifer depletion and salinization of irrigated soil.
Surface Water Removal
When surface surface water is removed, wetlands dry up, Estuaries (where rivers falls in oceans) become salty. In arid American Southwest it is uncommon that 70 % of water is withdrawn.
Aquifer Depletion
The over use of groundwater by humans cause the aquifers depletion. Aquifers can dry up if its use has been exceeded. The San Joaquin Valley has been sunk to 10 m due to aquifer depletion over past 50 years. Saltwater intrusion, mixing of seawater with freshwater aquifer occurs due to aquifer depletion.
Salinization of irrigated soil
When irrigation is done , it increases the productivity of soil but it also accumulates the salts in the soil that phenomenon is known as salinization. Saline soil causes the low or no productivity of soil and it is also not good or fit for crops yield.
