STREAMFLOW ANALYSIS AND MODELLING - Fundamentals of Hydrology

Geoscience Reference

In-Depth Information

Models such as PHABSIM have been used suc-

cessfully in many places around the world to advise

water managers on the best flow regime for particu-

lar aquatic species. It should be noted that this is

a physical approach to the problem, i.e. it takes

account of the physical flow regime of the river with

no consideration of water quality parameters. The

assumption is made that water quality does not

change with the proposed changing flow regime.

fully in many places around the world to achieve

this. They combine hydrological and ecological

knowledge to provide vital information to resource

managers.

ESSAY QUESTIONS

1

Find a scientific paper in the literature

that uses a hydrological model and

evaluate the type of model and its

strengths and weaknesses for the study

concerned.

SUMMARY

The analysis of streamflow records is extremely

important in order to characterise the flow regime

for a particular river. Hydrograph analysis involves

dissecting a hydrograph to distinguish between

stormflow and baseflow. This is often a precursor to

using the unit hydrograph, a technique using past

stormflow records to make predictions on the likely

form of future storm events. Flow duration curves

are used to look at the overall hydrology of a river

- the percentage of time a river has an average flow

above or below a certain threshold. Frequency

analysis is used to look at the average return period

of a rare event (or the probability of a certain rare

event occurring), whether that be extremes of

flooding or low flow. Each of the methods described

in this chapter has a distinct use in hydrology and

it is important that practising hydrologists are

aware of their role.

Computer modelling offers a methodology to

investigate hydrological processes and make pre-

dictions on what the flow might be in a river given

a certain amount of rainfall. There are different types

of models, with differing amounts of complexity,

but all are a simplification of reality and aim to

either make a prediction or improve our under-

standing of biophysical processes.

A key use of flow and hydraulic data is to assess

the needs of aquatic fauna within a river system.

This information is used by managers of regulated

rivers to set flow regimes that are beneficial, or

at least non-detrimental, to particular flow species.

Models such as PHABSIM have been used success-

2

Outline the limitations of the unit

hydrograph when used as a predictive

tool and attempt to explain its success

despite these limitations.

3

Describe the types of information that

can be derived from a flow duration

curve and explain the use of that

information in hydrology.

4

Explain why interpretation of flood (or

low flow) frequency analysis may be

fraught with difficulty.

5

Describe the data (and measurement

equipment) required for using the IFIM

approach to look at the habitat

requirements for a particular aquatic

species.