EQ2: What factors influence the hydrological system over short and long term timescales? Flashcards
What is teleconnections?
Climate anomalies which relate to each other at large distance
What is humbolt?
A cold, north bound ocean current at the west of South America
What is phytoplankton?
The base of several aquatic food webs which provide food for a range of sea creatures
What is thermocline?
The sharp boundary between the cold, deep water and the warmer upper layer
What is the UN definition of drought?
An extended period of time of deficient rainfall relative to the statistical multi year average for a region
What are the types of droughts?
-Meteorological = long term precipitation is much lower than normal
-Agricultural = insufficient soil moisture to meet the needs of crops
-Hydrological = deficiencies in surface and subsurface water supplies
-Socio economic = water demand for social and economic purposes exceeds water availability
What happens in a normal year?
-Trade winds from the equator blow wide and west across the Pacific
-The winds blow towards the warm water at the western Pacific
-Convectional uplift occurs as water nears the atmosphere
-Trade winds push the warm air westwards along the east coast of Peru
-The shallow position of the thermocline allows winds to pull water from below
What happens in a La Nina year?
-Stronger trade winds push warm water westwards increasing sea level in Indonesia and the Philippines
-Low pressure over the western Pacific becomes lower and high pressure over the eastern Pacific becomes higher
-This causes an increase in rainfall over southeast Asia and droughts in South America
-Trade winds strengthen due to increased pressure difference between the two areas
What happens in an El Nino year?
-Pressure systems, atmospheric circulation and weather patterns reverse
-Pilled up water that usually occurs in the west moves back east increasing sea levels in Peru
-Warmer waters develop in the eastern Pacific
-Low pressure forms due to rising air forming heavy rainfall over the eastern pacific
-The western Pacific creates drier conditions due to descending air leading to droughts in Indonesia and northern Australia
-India faces monsoon seasons
Case Study: Sahel region of Africa
-Semi arid region across Africa at the southern edge of the Sahara Desert covering 11 countries
-Decline in annual rainfall since the 1960s
-Could be due to anthropogenic climate change caused by air pollution generated in Europe and North America
-Region has one of the world’s highest poverty rates and development levels as well as one of the largest population growths
-Dry land ecosystems are converted into farmlands which are being overgrazed causing desertification
How do droughts impact wetland ecosystems?
-Loss of habitat
-Soil erosion
-Alter communities e.g. eliminating species or causing gaps in the food web
How do droughts impact forest ecosystems?
-Trees get disease e.g. 90% of Pinon pines died of beetle bark disease in the USA
-Increase in climate change due to the loss of a carbon store
-Reduces/slows tree growth
What are the types of flooding?
-Surface water = when intense rainfall doesn’t have time to infiltrate the soil
-Ground water = the ground is already saturated from previous rainfall
-Flash = floods with short lag times
-Jokulhlaup = glacial out burst flood
What are the human causes of flooding?
-Urbanisation = increases surface run off to rivers, shortens river lag time
-Deforestation = reduces interception and evapourtranspiration, increased surface run off leading to flash floods
-Floodplain drainage = draining floodplains reduces the natural storage capacity and when the land dries it shrinks so is more likely to flood
-Flooding mismanagement = can cause altercations in the drainage system and can affect downstream
What are the physical causes of flooding?
-Prolonged heavy rainfall = dependant on the cycle of the jet streams
-Monsoons = when 70% of the annual rainfall occurs in 100 days, 2000 people died because of this in Bangladesh and 250 million made homeless
-Intense storms = Pakistan received 9000mm of water in a week in July 2010
-Snow and ice = glacial outburst floods, melting snow
What are the socio economic impacts of flooding?
-3000 flood disasters since 1900-2010
-Disrupts income from tourists
-90% all flood deaths are in Asia
-Affects crops, livestock, agricultural infrastructure
-1900-2010 = 200,000 flood deaths and 3 billion affected
-Post flood morbidity due to water borne diseases
What are the environmental impacts of flooding?
-Can trigger breeding of species and encourage migration
-Pollution from nitrates and chemicals into aquatic habitats
-Recharge groundwater systems and fill wetlands
-Lead to over supplies of sediment which can cause eutrophication and can destroy aquatic habitats
What is positive and negative feedback?
Describes how a system responds to a change in inputs
-Negative = regulates the system and tries to keep it in a state of balance
-Positive = changes have a snowballing effect which can cause permanent long term changes
How will climate change impact the hydrological cycle?
-Intensification of the hydrological cycle
-Differential changes in the way the hydrological cycle operates within the worlds drainage basins
-Countries must deal with changes in water budgets which will impact how climate change is managed to secure water in the future
What are the impacts of short term climate change on water supplies?
-More frequent monsoon and cyclone events
-Increased intensity and frequency of droughts
-Decreased rainfall in many areas
-Greater rates of evapourtranspiration and desiccation of forest stores
What ways can we adapt to climate change?
-Stop wasting water
-Maintain plant coverage
-Improve irrigation techniques
-Give rivers more space
-Create 1.5 metres squared of infiltration area per sealed area to make it more permeable
