Deck 34- Water budgets, river regimes and storm hydrographs Flashcards
What is a water budget?
The water budget is the annual balance between precipitation, evapotranspiration and runoff. It represents the annual balance between inputs and outputs into a drainage basin.
What is a water budget used for?
-At a national or regional scale water budgets provide essential information about the amount of water that is available for human use (e.g. agriculture and domestic consumption)
-At a local scale water budgets can inform out available soil water (the amounts of water that can be stored in soils and is available for growing crops). It is very useful to farmers who can use it to identify when irrigation might be required.
How do you calculate a water budget for an area?
Precipitation (P) = Discharge (Q) + Evapotranspiration (E) +/- changes in storage (S)
What is the difference between water surplus and water deficit?
When precipitation is higher than discharge and evapotranspiration it result in water surplus.
Water deficit occurs when discharge and evapotranspiration are higher than precipitation
What state is the soil water moisture level in at ‘A’ in the graph and why?
Soil moisture surplus- precipitation is higher than potential evapotranspiration and stores have been refilled since the summer months
What state is the soil water moisture level in at ‘B’ in the graph and why?
Soil moisture utilisation- potential evapotranspiration is higher than precipitation levels so water stored in the soil is being used up without being replaced
What state is the soil water moisture level in at ‘D’ in the graph and why
Soil moisture deficit- potential evapotranspiration is higher than precipitation levels and all stored water in the soils have been used up meaning there is no longer enough water in the soils to sustain vegetation
What state is the soil water moisture level in at ‘E’ in the graph and why
Soil moisture recharge- precipitation levels are higher than evapotranspiration levels so stored can begin to be replenished during the early winter months
What is a river regime?
The annual variation in the discharge of a river or flow of a river at a particular point. Discharge is measured in cumecs (m3/sec)
What does a typical river regime look like in the UK?
In the UK the discharge of rivers is usually higher in winter months when precipitation totals are higher. In the summer discharges are usually lower and can sometimes even dry up completely.
What factors impact on the regime of rivers?
-The size of the river
-The amount of, seasonality and intensity of the precipitation
-The temperatures, with possible meltwater and high rates of evapotranspiration in the summer
-The geology and soils particularly their permeability and porosity
-The amount and type of vegetation cover
-Human activities aimed at regulating a river’s discharge
What is a storm hydrograph?
A Storm Hydrograph is a graph which shows how river discharge changes in response to a precipitation event.
What two variables are plotted on a storm hydrograph?
Storm hydrographs plot both precipitation totals from a storm event and discharge which allows geographers to analyse the relationship between the two variables
What are the characteristics of a flashy hydrograph? How does this impact on the risk of flooding?
When water is transferred quickly the lag time is shorter, the rising limb is steeper and the peak discharge is higher. As more water enters the channel faster there is an increased chance of flooding.
What are the characteristics of a subdued storm hydrograph? How does this impact on the risk of flooding?
When water is transferred more slowly the lag time is longer, there is a gentler rising limb and peak discharge is usually lower. As water takes longer to enter the channel more is lost on the way which decreases the chance of flooding.
What type of hydrograph does this show?
Flashy
What type of hydrograph does this show?
Subdued
What factors lead to a flashy storm hydrograph response?
Impermeable ground surfaces, steep relief, lack of vegetation, urbanised areas, high amounts of agriculture, areas with compact soils
What factors lead to a subdued storm hydrograph response?
Permeable ground surfaces, gentle relief, highly vegetated areas, less urbanisation/agriculture, less compact soils, reforestation
What are Sustainable Urban Drainage Systems (SuDS) and what do they aim to do?
Sustainable Urban Drainage Systems (SuDS) is a concept that aims to integrate water into urban planning and development.
It aims to design urban infrastructure that manages water sustainably, provide ecosystem services and enhances quality of life for urban residents whilst also reducing flood risk in urban areas
What are green SuDS solutions?
Green solutions- designing infrastructure to support and encourage the growth of trees in urban areas. This often includes investing below ground e.g. using tree pits or pavement support systems to support their growth, adding tree guards and climbing support systems and adding irrigation where needed. Trees reduce surface run off by 80% compared to asphalt/concrete
What are blue SuDS?
Blue solutions- involves adapting water flows and stores in an urban drainage basin. This can include adding small ponds, filter strips or attenuation basins to slow down the flow of water in peak flow. It can also include recycling of rainwater and investing in urban surfaces that are permeable e.g. porous paving
How have Newcastle University implemented SuDS?
-Newcastle University are carrying out in-site research into sustainable urban drainage at the Helix.
-Throughout the Helix site there has been an emphasis on creating green spaces including green walls and encouraging the growth of native trees/flowers. Irrigation systems have been used to support flower beds/trees and green walls have climbing structures to encourage upwards growth
-Behind the Helix is a drainage ditch which acts as an attenuation basin and a temporary storage of water after intense precipitation events
-Newcastle University has also invested in 13 trees planted in hard paving outside the Armstrong Building using tree pits and pavement support systems
