Lecture2 watershed approach dung

VFU-2016 Lecture #2: Watershed Approach Principles of Watershed management Dr Bui Xuan Dung- Department of Environment Management Why Watershed Approach? • 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 Irrigation Flood control Sediment transport and control Water shortages Water pollution Nutrient transport Fresh and marine water ecosystems 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? Image credit: NOAA Figures show dead zone near mouth of Mississippi River, Gulf of Mexico Image credit: APA News/NASA Natural disaster in Watershed How local hazards is related to upstream conditions?? Issues of spatial scale Land use in watershed Land use in watershed 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   Practices of resource use & management not depend solely on the physical & biological characteristics of WS How these factors are inter-related 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 Why Watershed Approach?   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 Organization of scale 10000 YR Volcanic activities Earthquakes 1000 YR 100 YR Tectonic activities Glacier activities Climate change Mass movement 10 YR Year Channel Forms Month Hydrologic regime and Water Quality Day Time Bedload and suspended sediment Single particle cm m 10 m km 10 km 100 km Relative spatial scale 1000 km 10000 km Watershed Assessment Learning later of our class • 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 Watershed Assessment Process 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 Step 3: Gather information identify and evaluate problems or concerns • Forest watershed • Agriculture watershed • Urban Watershed • • • • • • Land use Water quanlity and quality Forest management Agriculture Soil erosion Stream ecology 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 ...Why Watershed Approach? • Water is the fundamental agent that links all components (living and non-living) in watersheds • Watershed management generally revolves... Fresh and marine water ecosystems Why Watershed Approach?     Watersheds are among the most basic units of natural organization in landscapes The limits of watersheds are defined by topography... News/NASA Natural disaster in Watershed How local hazards is related to upstream conditions?? Issues of spatial scale Land use in watershed Land use in watershed Land use in watershed California, USA