Water and Carbon Pack 1

Human impact on the hydrological cycle (4)

• More people and wealthier people has led to changes in the water cycle

• Climate change also impacting water cycle

• Main uses for water are industry, agriculture and domestic use.

• Humans influence by taking water away from stores or flows and also indirectly through building urban areas or changing land uses from vegetation.

Cloud Seeding in Idaho - What is it

Strategy designed to encourage precipitation. Particulates, usually silver iodine, are released into the atmosphere and act as the hydroscopic nuclei that are required for rain and snow to occur. Water vapor accumulates around the particulates until they are heavy enough to fall as raindrops.

Cloud seeding in Idaho - impact (2)

In Boise, Idaho - local farmers rely on melting snow from mountains as a supply of water for irrigation.                                     

Increasing demand for water puts pressure on existing stores, but by enlarging the snowpack volume in winter through cloud seeding, it is hoped that farmers will have more water for irrigation.

Deforestation In Sierra Leone - what is it

Freetown is particularly vulnerable to flooding and mudslides. As the capital has grown, the city limits have crept up onto the surrounding hills. The Central Highlands, which overlook the city, have been deforested leaving soil exposed and weakened.

deforestation in Sierra Leone - Impacts

Without the vegetation to intercept the rainfall, infiltration rates decrease and direct overland flow increases, leading to shorter lag times and flooding. The roots of the trees also anchor the soil, reducing the chances of the devastating mudslides such as those seen in 2017.

Ogallala aquifer - what is it (2)

Ogallala aquifer provides around 30% of the groundwater used for irrigation in the United States.

Growing population and advances in automatic irrigation systems such as the center pivot irrigation method have led to water levels dropping by up to 150ft in some places of aquifer.

ogallala aquifer impacts

The rate of recharge can take either months or hundreds of years.

Natural flood mangement in Pickering, UK - what is it (5)

Town in UK with flooding problem. Aims to use natural processes and features to help manage river discharge, these include:

• Constructing low level bunds

• Planting more trees

• Restoring woody debris dams in small streams

• Restoring wetlands

Natural flood management Pickering, UK - Impact

Increases interception and infiltration rates in the upper parts of the drainage basin, increase water storage within tributaries and improve river flow within the town.

Houston infiltration rates and aquifer abstraction - what is it

Houston's population has doubled to 2.3m people in last 50 years. As a result, the physical limits of the city have been pushed outwards. This has led to the loss of 100,000ha of wetland and the building of over 7,000 homes on floodplains. Additionally, increased abstraction from three main aquifers has led to 10-25mm of subsidence per year.

Houston infiltration rates and aquifer abstraction - impacts

Without wetlands to act as a natural sponge and the full floodplain to provide space for infiltration, Houston suffered substantial flooding after Hurricane Harvey.

GERD in Ethiopia - What is it (2)

Dam designed to mitigate effect of hydrological extremes by reducing a river's discharge during periods of increased precipitation, as well as by releasing stored water in periods of drought.

GERD construction began in April 2011

GERD in Ethiopia - Impact (3)

Hydroelectricity to feed into national grid of Ethiopia with surplus during rainy seasons going to Sudan. Main impacts on drainage system are:

• increase in evaporation rates 

• rise in surrounding water table

Climate change effect on water cycle - What is it (2)

Human influenced climate change is increasing the risk of both intense rainstorm events and extreme droughts.

The hydrological cycle is affected due to the many processes within drainage basin being susceptible to temperature change.

Climate change effect on water cycle - impacts

In places where temperatures are rising, evapotranspiration rates will increase and, since warmer air is able to hold more moisture this may lead to more storm events.    Conversely, higher evaporation rates may lead to drier soils. When rains do fall, much of the water will run off overland increasing the likelihood of flash floods.