Gabriela Aguiar & Maria Fernanda Suarez

Is converting salty seawater to freshwater the answer? Chapter 13 Section 5 We can convert salty ocean water to freshwater BUT the cost is high, VERY COSTLY The resulting salty brine must be disposed of without harming aquatic or terrestrial ecosystems.

Desalination

 Heating water until it evaporates leaving behind the salts and condenses as fresh water.  The action of purifying a liquid by a process of heating and cooling. This is an example of how the process occurs

 Uses high pressure to force saltwater through a membrane filter with pores small enough to remove salt. This is an example of how the process occurs

 Desalination: involves removing dissolved salts from ocean water or from brackish (slightly salty) water in aquifer or lakes for domestic use.  Distillation: is a method for desalinating water. Heating water until it evaporates leaving behind the salts and condenses as fresh water.  Reverse osmosis ( microfiltration): is another method. Uses high pressure to force saltwater through a membrane filter with pores small enough to remove salt. Removing salt water from seawater seems promising but is costly

 Saudi Arabia has the world’s largest number of desalination plants.  The United States has the world’s second greatest desalination capacity.

 1. High cost and high energy footprint.  It takes a lot of energy to desalinate water with distillation requiring about ten times as much energy as reverse osmosis requires.  2. Pumping large volumes of seawater through pipes and using chemicals to sterilize the water and keep down algal growth  kills many organisms.  3. Desalination produces a large number of briny wastewater that contains lots of salts and other minerals.  This makes increase the salinity of ocean waters. Three major problems with Desalination

How can we use water more sustainably? Chapter 13 Section 6 We can use water more sustainably by o cutting water waste o Raising water prices o Slowing population growth o Protecting aquifers, forest and other ecosystems that store and release water

Reducing water waste has many benefits.

The causes of Water waste “WHY DO WE HAVE WATER WASTE?”

 Irrigation: the artificial application of water to the land or soil.  It is used to assist in the growing of agricultural crops, maintenance of landscapes, etc..  About 60% of the irrigation water applied throughout the world does not reach the targeted crops. We can cut water waste in Irrigation

 Delivers far more water than is needed for crop growth and typically loses 40% of the water through evaporation., seepage, and runoff.  This wasteful method is used on 97% of China’s irrigated land. FLOOD IRRIGATION METHOD:

 The most efficient way to deliver small amounts of water precisely to crops.  It consist of a network of perforated plastic tubing installed at or below the ground level.  Current drip irrigation systems are costly BUT they drastically reduce water wastes; 90-95% of the water input reaches the crops.  It is used on just over 1% of the world’s irrigated crop fields  4% of those in the United States.  This percentage rises to  90% in Cyprus,  66% in Israel, and  13% in California. Drip or Trickle Irrigation MICROIRRIGATION METHOD:

Solutions for Reducing Irrigation Water Waste

 Rainwater harvesting:  another simple and cheapest way to provide water for drinking and for growing crops throughout most of the world. (for irrigation) Developing Countries Use Low-Tech Methods for Irrigation

 “The frog does not drink up the pond in which it lives.” We need to use water more Sustainably

LETS CHANGE THE WORLD

How can we Reduce the Threat of Flooding? Chapter 13 Section 7

 Floodplain -A flood happens when water in a stream overflows its normal channel and spills into the adjacent area.  Floods provide several benifits:  They have created the world’s most productive farmland by depositing nutrient-rich silt on floodplains.  Recharge groundwater and help refill wetlands, thereby supporting biodiversity and ecological services. FLOODS KILL THOUSANDS OF PEOPLE EACH YEARAND CAUSE TENS OF BILLIONS OF DOLLARS IN PROPERTY DAMAGE. Some Areas get TOO much Water from Flooding.

 Human activity. (Especially on hillsides) Removal of Water-absorbing Vegetation

Case Study! Pg.339

 Channelizing streams reduces upstream flooding.  BUT it also:  Eliminates aquatic habitats  Reduces groundwater discharge  Results faster flow Which can increase downstream flooding and sediment deposition. We can reduce flood risks:

 One of the most important ways to reduce flooding is  To perserve existing wetlands  Restore graded wetlands  To take advantage of the natural flood control they provide in floodplains.  This helps protect biodiversity and to restore degraded ecological services provided by these awuatic ecosystems. Reduce flooding

 THINK CAREFULLY OF WHERE WE CHOOSE TO LIVE  Many poor people live in flood-prone areas because they have no where else to go. FLOOD RISKS