Lecture2 watershed approach dung

VFU-2016 Principles of Watershed management Lecture #2: Watershed Approach Dr.. • Water is the fundamental agent that links all components living and non-living in watersheds • Waters

VFU-2016

Principles of

Watershed management

Lecture #2: Watershed Approach

Dr Bui Xuan Dung- Department of Environment Management

• Water is the fundamental agent that links all components (living and non-living) in watersheds

• Watershed management generally revolves around

water as a central theme

Why Watershed Approach?

 Watersheds are among the most basic units of natural organization in landscapes

 The limits of watersheds are defined by topography

and the resulting runoff patterns of rainwater

 The entire area of any watershed is therefore

physically linked by the flow of rainwater runoff

 Consequently, processes or activities occurring in one portion of the watershed will directly impact

downstream areas (land or water)

Why Watershed Approach?

 When detrimental activities like clear-cut deforestation occur, negative impacts are carried downstream in the form of eroded sediments or flooding

 Poor agricultural land management

activities like excess fertilizer application convey negative impacts to downstream areas in the form of eutrophication and

possible fish kills

Eutrophication

• Eutrophic-

– Slow-flowing stream, lake or estuary enriched

by inorganic plant and algal nutrients such as phosphorus

– Often due to fertilizer or sewage runoff

What happens downstream?

Figures show dead zone near mouth of

Mississippi River, Gulf of Mexico Image credit: APA News/NASA Image credit: NOAA

Natural disaster in Watershed

How local hazards is related to upstream conditions??

Issues of spatial scale

Land use in watershed

California, USA

BC, Canada

Issues of temporal scale

When hazards is

occurred with respect

to land use changes??

Road impacts

Stream channel

Hydrological connection

No hydrological

connection

Road, skid trail runoff

Watershed Water Cycle

Impacts of Management

Effect of upstream changes on

downstream systems

 Are these disasters preventable ?

 Different approaches may be needed:

• Modifying Natural Systems?

• Modifying Human Systems?

• A combination?

 Land use planning?

 What time and space scale we should consider?

Links between

physical processes and biological

processes

Hydrological

Processes Geomorphic processes

Biological Processes

WSM: a global perspective

management do not depend solely

on the physical & biological

characteristics of WS

can best be illustrated ?

Watershed management

a global perspective

• Land & water management is the major environmental issue

• Water demands > supplies (17%)

• Next 20-25yrs  2/3 pop water shortage

• Land scarcity  forest cut

• Desertification

• Hydrometeorological extremes, role of

watershed management

 Recognizing that enhanced interactions

between seemingly separate systems and

organisms occur within watershed areas, both

scientists and resource managers have called

for management programs to be organized at the watershed level

 By working in concert with nature in this way,

we might manage resources in an integrative

fashion that avoids some of the many past

failures that were brought by not recognizing or considering the larger-scale (upstream to

downstream) impacts of any one management decision

Why Watershed Approach?

Single particle

Hydrologic regime and Water Quality

Channel Forms

Mass movement

cm m 10 m km 10 km 100 km Time

Tectonic activities Glacier activities

Organization of scale

Watershed Assessment

• A critical step in developing and

implementing a watershed management plan

• Knowing important aspect of watershed

• Evaluating how various land use can

affect the environmental and economic health of the watershed

Learning later of our class

Step 1: Develop an approach for the

assessment

Step 2: Gather information for watershed

(general information)

Step 3: Gather information identify

and evaluate problems or concerns

Step 4: Evaluate your data

Step 5: Suggest Watershed management

Watershed Assessment Process

Step 3: Gather information identify and evaluate problems or concerns

• Forest watershed

• Agriculture watershed

• Urban Watershed

Step 5: Suggest Watershed

management

• Specific preservation and restoration goal

• Specific land use planning

• Area need to be preserved

• Specific actions for solving water and

sediment problem