Water Scarcity and Water Quality

Possible essays: environmental consequences of agricultural activities on water quality, case study of one internationally shared water resource and the role of different stakeholders in attempting to find a resolution

Water Quality + Factors

Water Quality + Factors

WHO estimates that 4 million deaths occur yearly from water related diseases: Cholera, hepatitis, malaria, other parasitic diseases

Factors: poor infrastructure, poverty, war + conflict, pollution(sewage, industry, agriculture), misuse, water-borne diseases, geology, dams, no testing, other abstraction

Irrigation Methods Worst to Best

Surface/Flood: 90% of irrigated areas use this

Sprinkler: 5% use this, applying water under pressure

Drip/Trickle: applying water directly to soil area, ideally at rate of consumption

Subsurface: flooding water underground and allowing it to come to roots via capillary action

Condensation: closed-loop, solar operated system that condenses humidity in the air on the external surface of pipes containing cold-running water

Increase in Irrigation

8 billion mouths to feed(+8 million yearly), Green Revolution, increased use of marginal land, technological advancements allow access to deep aquifers, greenhouse + hydroponics, climate change, growing middle class, fodder crops, biofuel, fast fashion + cotton

Ogallal Aquifer

Under the Great Plains, used 8x as fast as it is recharged, 33% of all food grown in US is grown with usustainable water use

Saudi Arabia + Aquifers

Fossil aquifer discovered in 1990s, created wheat, self-sufficient for 20 years, aquifer dried up

Salinisation and Saltwater Intrusion

Water evaporates while salt is left to build up

At coastal wells: interface moves towards well due to rising sea levels and/or overextraction

Impacts of Irrigation on the Environment

Waterlogging and salinisation, water-borne diseases, usustainable use of groundwater, water pollution from nutrients or pesticides, diverted water impacts downstream, land subsidence from aquifer withdrawals, dams and reservoirs

Impacts of Agriculture on Water Quality

Slurry → misture of water and manure, sprayed on fields, nitrogen runoff

Fertilisers(NPK) → eutrophication

Pesticides → kills insects, biomagnification(DDT), runoff

Silage Juice → humic acid, fed to cows

Herbicide → kills plants, runoff

What’s Wrong with Lawns?

30-60% of US urban freshwater is used on lawns

10x the amount of pesticides and fertilisers per acre as farmers use on their crops

2005 → American residential lawns take up 128,000km2, same size as Greece

Drought

Normal, recurrent feature of climate, occurs in virtually all areas, temporary condition, result of when there is less than normal precipitation over an extended period of time, only becomes a crisis when we consider the demand people put on their water supply

Causes of Drought

Human: deforestation, overpopulation, industrial/agricultural demands, economic development

Physical: rising temperatures, falling rainfall

El Niño

wind usually creates Walker Circulation west-ward, creates upwelling along South America and fish, occasionally stops + creates drought in SE Asia and Oceania + flooding in South America

Colorado(Case Study): Details

Exotic river(headwaters lie in a humid environment and runs through an arid region)

supplies water to ~40 million people, irrigates 1.5 million hectares of farmland

runs through Colorado, Wyoming, Utah, New Mexico, Arizona, Nevada, California, Mexico(7 states)

Phoenix + Tucson(Central Arizona Project), LA + SAN BERNADINO(Colorado River Aqueduct), Las Vegas, Nevada, SAN DIEGO

Colorado(Case Study): Colorado Compact

1922, 7 states, averts federal involvement, water divided between upper and lower states, U agreed to provide L with 93km3/y over a 10 year period, annual flow was not in excess of 183km3 per year, later updated, didn’t involved Mexico

Colorado(Case Study): Minute 319

20th November 2012, governments of US and Mexico overhauled shares + agreed to share excesses and shortages, during drought less water to Mexico, during plenty Mexico gets more + can store it in US, allocated water to restore delta, only been in drought since 2012

Colorado(Case Study): Delta

Barely exists, river hasn’t reached sea since 1998, Mexico granted 1850 million m3 in exchange for supplies from Rio Grande in Texas

Colorado(Case Study): All American Canal

Forms part of border, takes last bit of water, largest irrigation canal in the world, carries up to 850m3/s, irrigates Imperial Valley, formerly a Sonoran Desert ecosystem, drains into Salton Sea

Nile(Case Study): Details

Longest river in the world(6,650km)

White Nile(15%) + Blue Nile(85%) converge in Khartoum

flows through 11 countries(DRC, Burundi, Rwanda, Uganda, Kenya, Ethiopia, Sudan, Egypt, Eritrea, Tanzania, South Sudan)

10% of Africa is in the drainage basin

257 million live in the basin

Nile(Case Study): 1929 Nile Water Agreement

Colonial treaty between UK, Egypt, and Sudan, gave Egypt 57% of the water, gave Sudan 5%, with other countries getting nothing

Nile(Case Study): 1959 Nile Water Agreement

Between Sudan and Egypt, Nile flow was agreed to be 84 billion m3 measured at the Aswan High Dam, Nile to be shared at 18.5 and 55.5 billion m3 respectively

Nile(Case Study): Entebbe Agreement

2010 agreement between Ethiopia, Kenya, Uganda, Rwanda, and Tanzania, and later Burundi, calling for water redistribution, rejected by Egypt and Sudan