An Introduction to Hydrology L.O. To understand the drainage basin hydrological system Lesson 1 The Drainage Basin Hydrological Cycle

The Drainage Basin Hydrological Cycle Drainage Basin Precipitation Percolation Stemflow Surface Storage Can you write a dictionary definition for these words?

Precipitation The fallout of water drops or frozen particles from the atmosphere (McGraw-Hill Dictionary of Environmental Science, 2008)

Surface Storage The part of precipitation retained at the ground surface (McGraw-Hill Dictionary of Environmental Science, 2008)

Stemflow ‘The flow of water down the trunk or stem of a plant’ (wikipedia) ‘The process that directs precipitation down plant branches and stems’ (geography-dictionary.org)

Drainage Basin ‘The area of land drained by a river and it’s tributaries’ (Barker, Redfern and Skinner, p.13, 2008) Where’s the watershed?? A drainage basin may also be called a ‘catchment’

The Drainage Basin Hydrological Cycle The Hydrological Cycle There is a fixed amount of water circulating in our atmosphere and on its surface. There are no exchanges outside the earth and its atmosphere. It is therefore a CLOSED SYSTEM, which means that there are no INPUTS or OUTPUTS of water but only of energy. Water is continuously cycled between the oceans, the land, and the atmosphere as the GLOBAL HYDROLOGICAL CYCLE.

Draw a copy of Fig 1.4 Can you label any of the arrows to show the processes by which water is moving?

The Drainage Basin Hydrological Cycle The part of the hydrological cycle that occurs within a drainage basin. The hydrological cycle is a closed system but the drainage basin is an open system with inputs, and outputs as well as transfers and stores.

The Drainage Basin Hydrological Cycle Precipitation Can you construct your own drainage basin hydrological cycle? Infiltration Percolation Interception Throughflow Stemflow Use the cards to construct your own version of the DBHC Draw arrows between the cards to show how they are linked You must be able to justify why you put each card in a particular place. When you’re done colour code each card to show if it’s an input, store, transfer or output End!

The Drainage Basin Hydrological Cycle Copy and complete the following paragraphs into your notes: The drainage basin (or catchment) is the area of land drained by a __________ and ___ ___________. An imaginary line called the __________ separates one drainage basin from another. This follows a ridge of highland; any rain falling on the other side of the ridge will flow into another river in the adjacent drainage basin. The drainage basin hydrological cycle is the part of the hydrological cycle that occurs within a _______ _______. Unlike the hydrological cycle it is a closed/open system. The DBHC is made up of ______ and ______, which can vary greatly over _______, ________ and ________.

The Drainage Basin Hydrological Cycle What could I be asked in the exam? Give a detailed definition of any of the key words in the DBHC Fill in gaps on a diagram of the DBHC Explain how human activities could modify the DBHC

ThroughflowEvaporationOverland flow TranspirationGroundwater flowPercolation Vegetation Storage Throughfall and Stemflow Surface Storage

The movement of water over the surface of the ground to rivers Water changes from a liquid to a gas and is returned to the atmosphere Evaporation is facilitated by energy from the sun Water drains down through rocks towards the water table The water table is the upper level of groundwater. Water flows through rocks towards the river. This is affected by rock type e.g. if the rock is permeable or not. The part of precipitation retained at the ground surface Precipitation drips through vegetation to the ground Precipitation runs down the stems of plants or trunks of trees to the ground. Water moves horizontally through the soil under towards rivers. Normally happens when the soil is completely saturated with water. Water evaporates from inside vegetation and is returned to the atmosphere. Plants can control the rate of transpiration by opening and closing their stomata Water is stored within plants and trees.

Groundwater flow (Base flow) Groundwater StoragePrecipitation Channel Storage Infiltration River Runoff Channel FlowInterceptionSoil Water

Water and ice that fall from clouds into the drainage basin. It can take many forms and vary greatly over time and space Water is stored in permeable rocks below the surface of the ground Water flows through rocks towards the river. The rock type can affect the rate of flow The total discharge of water from the drainage basin via its’ main river The process by which water enters the soil The rate can be affected by factors such as soil type, soil saturation and duration of rainfall Water is stored in a river It is the amount of water stored in a river at a particular instant. Water is stored in the soil Precipitation is trapped or stored temporarily on vegetation Water flows in a river This is the most efficient means of removing water from a drainage basin

Water flows through rocks towards the river. The rock type can affect the rate of flow Water is stored in permeable rocks below the surface of the ground Water and ice that fall from clouds into the drainage basin. It can take many forms and vary greatly over time and space Water is stored in a river It is the amount of water stored in a river at a particular instant. The process by which water enters the soil The rate can be affected by factors such as soil type, soil saturation and duration of rainfall The total discharge of water from the drainage basin via its’ main river Water flows in a river This is the most efficient means of removing water from a drainage basin Precipitation is trapped or stored temporarily on vegetation Water is stored in the soil

Learning Outcomes All will be able to describe the main features of the DBHC and define most of the key processes. Most will be able to draw a sketch of the cycle, define all the key processes within in and explain how they are interlinked. Some will be able to explain the spatial and temporal variations that exist and explain how human activities can affect specific processes within the cycle.