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The water budget made SIMPLE + essential water facts

    Are you wondering what the water budget is and why it is important? Then you have come to the right place! In this article I outline what the water budget is, why the water budget is important and how to calculate the water budget. Ready to learn more? Read on…

    What is the water budget?

    The water budget is a way to track the movement of water through the hydrological cycle.

    It is like a bank account for water, where we keep track of how much water is coming in and going out of a particular area over a period of time.

    The inputs to the water budget include precipitation, which is the amount of water that falls onto the land, and any water that is imported into the area through rivers or underground aquifers.

    The outputs include evaporation, which is the amount of water that is returned to the atmosphere through the process of evaporation from the soil, plants, and other surfaces, and the amount of water that leaves the area through rivers and groundwater flow.

    By tracking these inputs and outputs, we can understand how much water is available in a particular area, and how it is being used and replenished over time.


    Why is the water budget important?

    The water budget is important because it helps us understand the availability and movement of water in a particular area.

    By calculating the inputs and outputs of water in a region, we can determine if there is a water surplus or deficit. This information can be used to manage water resources, such as for agricultural irrigation or municipal water supply.

    Additionally, changes in the water budget over time can indicate changes in climate or land use, which can have significant impacts on ecosystems and human populations.

    Therefore, understanding the water budget is crucial for managing water resources sustainably and protecting the environment.

    Where is Earth’s water stored?

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    Here’s a breakdown of where Earth’s water is stored:

    • Oceans: About 97.5% of Earth’s water is stored in oceans, which are also the largest bodies of water on our planet.
    • Ice caps and glaciers: Around 1.7% of Earth’s water is locked up in ice caps and glaciers, mostly in the polar regions.
    • Groundwater: Roughly 0.63% of Earth’s water is stored underground in the form of groundwater, which is water that fills the gaps and spaces between rocks and soil.
    • Lakes and rivers: Only 0.013% of Earth’s water is stored in freshwater lakes and rivers.
    • Atmosphere: A small fraction of Earth’s water, around 0.001%, is present in the atmosphere in the form of water vapor.
    • Living organisms: Water is also stored within living organisms, such as plants and animals.

    It’s worth noting that while 70% of the Earth’s surface is covered by water, most of it is not readily available for human use due to its saltiness, location in ice caps or underground aquifers, or other factors.

    Therefore, managing and conserving freshwater resources is critical for sustaining human and ecosystem health.

    The water budget graph

    water budget

    The water budget graph shows the balance between water that enters and leaves a particular region over time. It is a way of tracking the amount of water in a particular area and how it changes.

    The graph typically shows the following:

    • Precipitation (the amount of water that falls on the area)
    • Evapotranspiration (the amount of water that is lost to the atmosphere by evaporation from the ground and transpiration from plants)
    • Runoff (the amount of water that flows off the area)

    By comparing these values, we can determine if an area is experiencing a water surplus (more water is entering than leaving) or a water deficit (more water is leaving than entering), which is important information for managing water resources.

    The water budget equation

    To calculate the water budget, you need to consider the inputs and outputs of water in a particular area.

    The inputs are the sources of water such as precipitation, which is the amount of water that falls as rain or snow, and inflow from other areas.

    The outputs are the ways that water leaves the area, such as evaporation and transpiration, which is the process where water is taken up by plants and released back into the atmosphere. Additionally, water can leave the area through surface runoff, which is water that flows over the ground surface and enters rivers or streams, or through groundwater flow, which is water that moves through permeable rock underground.

    To calculate the water budget, you subtract the total outputs from the total inputs. If the result is positive, then the area has a surplus of water, meaning that there is more water entering the area than leaving it. If the result is negative, then the area has a deficit of water, meaning that there is more water leaving the area than entering it. If the result is zero, then the area is in a state of water balance, meaning that the amount of water entering and leaving the area is equal.

    The water budget equation is as follows:

    P = Q + E +/- Changes in storage

    To do this equation you must understand the following:

    • Precipitation (P)
    • Runoff (Q)
    • Evapotranspiration (E)

    Water budget FAQs

    There are many questions that people are asking about the water budget. I have listed these below for you, along with answers.

    Does the water budget have a fixed global value?

    No, the value of the water budget varies from region to region, depending on the climate, topography, and other environmental factors.

    Is the water budget always balanced?

    In an ideal scenario, the water budget should always be balanced, meaning that the amount of water that enters a system (precipitation, infiltration, etc.) is equal to the amount that leaves (evaporation, transpiration, runoff, etc.). However, in reality, imbalances can occur due to factors such as human activities or extreme weather events.

    Is the water budget affected by human activities?

    Yes, human activities such as deforestation, urbanization, and irrigation can affect the water budget by altering the natural balance of inputs and outputs.

    Can the water budget be used to predict droughts?

    Yes, by analysing the water budget of a region, it is possible to predict the onset of drought conditions if the output exceeds the input for an extended period of time.

    Is the water budget a useful tool for water management?

    Yes, by monitoring the water budget, water managers can make informed decisions about water allocation, conservation, and infrastructure development to ensure sustainable water use.

    Essential facts about water

    Now that you understand what the water budget is, lets take a look at some interesting, yet essential facts about water…

    1. Water is a molecule made up of two hydrogen atoms and one oxygen atom and is essential for life as we know it.
    2. About 71% of the Earth’s surface is covered in water, mostly in the form of oceans and seas.
    3. Despite the abundance of water on Earth, only about 2.5% of it is fresh water, and much of that is not easily accessible for human use.
    4. Water is the only substance on Earth that exists in all three states – solid, liquid, and gas – at temperatures and pressures that are commonly found on the planet.
    5. Water has a very high specific heat capacity, which means it can absorb and release large amounts of heat energy without changing temperature too much. This helps regulate the Earth’s climate and keep temperatures stable.
    6. Water is a universal solvent, which means it can dissolve a wide variety of substances, making it an important agent for chemical and biological processes.
    7. The human body is about 60% water, and it plays a crucial role in regulating body temperature, transporting nutrients, and removing waste.
    8. Water is a renewable resource, but many parts of the world are facing water scarcity due to overuse, pollution, and climate change.
    9. The hydrological cycle, also known as the water cycle, is the continuous movement of water between the Earth’s surface, atmosphere, and underground. This cycle helps regulate the Earth’s climate and provide freshwater for ecosystems and human use.
    10. The United Nations has declared access to clean water and sanitation a basic human right, but many people around the world still lack access to safe drinking water and adequate sanitation facilities

    The water budget: To conclude

    As you will now understand, being able to understand and calculate the water budget is essential in managing our resources and it an important part of managing the global and local hydrological cycle.

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