case studies

Question 1

Nile delta

Answer 1

The delta
- Home to 50M ppl, ⅔ of pop
- 60% of Egypt’s food supply produced here
- Stretches from northern Cairo into 25 000 km2 farmland fed by Nile branches
- Growing pop extracted supplies, polluted water with toxins and impurities → Nile barely reaches end of delta
- One of the most fertile lands in the world
Problems
- Suffering from environmental crises including flooding, erosion, salination, industrial and agricultural pollution, coastal urban encroachment
- In some areas erosion is up to 100m/year
- Pop expected 83M → 110M in 2 decades
- Annual deposits from floods no longer reach delta (Aswan High Dam: less fresh water and floods to keep salt water at bay)
- climate change: ↑evap, ↑demand and water use upstream
- 1 m rise in sea level would drown 20% of delta, farmers would lose $1000/1 C rise in T
- Nile reaching delta is predicted to drop 70% in next 5 years

Question 2

Aswan high dam

Answer 2

Advantages
- Flood and drought control
- Irrigation: 60% used for, up to 4000 km of desert
- Hydroelectric power: 7000 Mkw/year
- Improved navigation
- Recreation and tourism: $500 M to country economy/year
Disadvantages
- Water losses: provides half expected amount
- Salination: crop yields decreased by ⅓ on area irrigated by dam
- Groundwater changes, ↑, secondary salination
- Displacement of pop: 100 000 removed
- Drowning of archaeological sites
- Seismic stress: earthquake november 1981 (H2O ↑ seismic activity ↑)
- Deposition within lake (infilling 100 M tonnes/year)
- Channel erosion on bed: ↓25 mm in 18 years. Erosion of Nile Delta: 2.5 cm/year
- Loss of nutrients: 1008M/year by commercial fertilisers to make up
- Decreased fish catches and sardine yield ↓95%, 3000 jobs lost
- Diseases spread, eg Bilharzia

Question 3

Aral sea

Answer 3

• Began shrinking in 1960s when Soviet irrigation schemes started to take water
• By 1994 shoreline fell 16m, surface area declined 50%, volume reduced by 75%, salinity increased 300%
• Salinity killed fishing industry, ↓soil fertility, frequent dust storms ruining cotton production
• H2O polluted by pesticides and fertilisers
  air quality affected by dust and salt: noticeable rise in respiratory and stomach disorders: over 40 years shoreline left about 45 M metric tonnes of contaminated dust

Question 4

Kissimmee river restoration

Answer 4

Impacts of channelisation
- Loss of 200-1400 h of wetlands
- A 90% ↓ wading bird and waterfowl usage
- Less recharge of aquifers: groundwater more saline
- Pre-canal average flow: 0.42 m/s to 0.05 m/s
- During floor water stays in drainage basin: 11 days to 1 day
Kissimmee
- 165 km meandered through central Florida
- Floodplain 5 km wide, inundated for long periods by heavy seasonal rains
- Plants, wading birds, fish thrived
- Deepen,straighten,widened channel 1962-71, 90km, 10m deep canal
- To provide outlet for draining floodwaters from developing upper Kissimmee lakes basin and to provide flood protection for land adjacent to river
Restoration
- Sustainability concerns: massive restoration scheme
1999-2015: 100 km2 river and associated floodplain wetlands
- Channelisation: backfilling bd half of flood control, remains in residential area
$400 (initial channelisation: $20M) - state of Florida and federal gov
- Benefits: high H2O level supports natural ecosystems, decreased nutrient flow downstream, species returned, some n. Tripled, dissolved O2 doubled, allowed recreational usage

Question 5

Bangladesh flooding 1998 sept 7

Answer 5

Bangladesh
- Low lying: 60% less than 6m above sea level
- Ganga, Brahmaputra, Meghna rivers meet: avg gradient is 6 cm/km
- Country drains an area 12 x its size
- High frequency of floods and cyclones
- Ganges drainage system carries 520 million tonnes of sediment/year, about 20% is forest, 6 dams on Ganga river
- Area: 143998 km2, pop: 166 M , age: 51% below 25 yrs, dens: 1161/km2 , employment: 47%, lit: 58.8%
causes
- High plateau of Tibet: source of Brahmaputra derives from snow and glacier melt
- Ganga plain is one of the largest lowland area with intense agriculture
- Himalayas, highland: topography, snowmelt, deforestation, high river discharge, vegetation, land use, sediment transport, type and intensity, heavy monsoon rains, orographic effect
- Indian plains, lowland: monsoon, construction of embankments and other structures, increased discharge, sediment transport, floods, Farakka barrage
- Bangladesh floodplains, lowland: high tides, high discharge, overflow of water courses, rising of mean sea level, backward flows, synchronisation of peak flows, riverbank erosion, old and changing of river courses, siltation, soil saturation, monsoon, water-logging, impeded drainage due to high water levels in rivers, impermeable soils, disappearance of wetlands, poorly planned embankments breached, flat topography, low channel gradient, geological depression