Topic 3: The Hydrological Functions of Forest

Introduction

Many forests occur in upland areas, and so knowing how water flows down a slope is important, as is a knowledge of what happens when trees on that slope are removed. Slope hydrology affects the actions that can be taken on slopes, with amount of care needed increasing as the slope angle increases. Water movement on slopes can trigger some of the geomorphological processes discussed in the final topic of this module, and so understanding how the movement occurs is important. That movement also plays an important part in determining where and when floods will occur, and how trees and forests interact with the magnitude and frequency of floods.

The amount of water that is available to a forest is dependent on the hydrological cycle. So an understanding of the basic components of this cycle is essential if a manager is to understand how forests and water interact. All plants need water to grow and forests utilize substantial amounts of water. A variety of processes are involved, and in this topic you will learn how our understanding of the close connections between the atmosphere and forests is growing. These processes occur at a range of scales, from small catchments to entire continents, and human activities are affecting all scales. For example, deforestation in the Amazon Basin is having an effect on the way that water is cycled across the whole Basin.