Virtual Mekong Basin

Analysis of the suite of issues confronting the Mekong basin poses information challenges, from the management and analysis of complex data to conveying the results to (non-technical) Decision Makers and a general public. The incorporation of more sophisticated information management systems, from data acquisition, distribution, and visualization into “cyber-infrastructure” could be an important next step. The metaphor is the development of a ‘Virtual Mekong Basin” (VMB), where basin attributes are examined and summarized digitally and then visually.

A logical place for the development of a VMB to start is by identifying the “big” driver questions, and then structuring the “engine” to providing the solutions for, or at least to address, those questions. The “big” questions –is the Tonle Sap filling up? Will the Delta vanish in the future? What happens to fisheries? – must be answered through the development of cross-sector knowledge.  The challenge now is to define those questions, and do it in a manner that will lead to the answers, which then are communicated via the VMB. Each set of process questions addresses a particular thematic area.

Basin Environment

  • How is the basin "built?" Geomorphology (geology, riverbed, deep pools)
  • What are historical, current, and future conditions for landuse, landcover and fisheries habitat?

Water & Water Resources

  • Where does water come from in the Mekong, and how is it distributed across the landscape? (Stream water, precipitation, ground water, surface flow, overall water balance, flood/drought, water quality, largest water users & irrigation)
  • What will happen with landuse and climate change?

Sediment Movement

  • What is the origin of the Mekong sediments, and how do they move? (suspended load, erosion, deposition, balance)
  • Why do riverbanks move, and what can be done about it?

Carbon Balance

  • What is the carbon balance of basin forests, and their carbon trading potential?
  • How does carbon move from land to the river and reservoirs, and to the atmosphere?

Hydropower

  • How will existing and future reservoirs effect the flow regime downstream?
  • Will the reservoirs fill up with sediments?

Fisheries

  • Why do fish need floods and deep pools? (Migration, Spawning, Catch, balance)
  • Can Mekong fish co-exist with hydropower?

Agriculture & Forestry

  • How have agriculture and forestry changed over the years? (floods, irrigation)
  • Will agricultural output change because of climate change and increased CO2?

Navigation

  • What is the impact of navigational channel rock blasting?
  • Is the Tonle Sap navigational channel sustainable?

Mining and Energy

  • What are the impacts of mining?
  • What is the balance between renewable and non-renewable energy sources?

Socio-economic

  • Where are the most vulnerable people living, and how dependent are they on natural resources?
  • How much will people benefit from hydropower versus fisheries, agriculture, forestry, and mining? How much development is needed to sustain population growth?

Determining how the landscape structure (topography, vegetation, soils) and climate interact to produce water discharge regimes in the Mekong is the first step towards understanding how change will affect the basin. To do this, we implemented the Variable Infiltration Capacity (VIC) model, at 1/12 degree (~8 km) spatial resolution for the entire Mekong basin, for the period 1979-2000 (as described in Costa-Cabral et al. 2007; Hydrol. Processes). The climate regime is shown here superimposed on the topography.

Annual Precipitation Average
Annual Precipitation Average

Land cover classifications were derived from multiple satellite datasets. For example the percent of agriculture in each grid cell is illustrated here (the lower layer), related to soil moisture (below).

Mekong Basin Annual Precipitation
Mekong Basin Annual Precipitation 3

The model is very effective at reproducing the observed hydrographs across the Mekong. Here is an example for several stations, on the Mekong mainstem and tributaries, using precipitation data from the Tropical Rainfall Measurement Mission (TRMM).

Mekong Hydrographs
Mekong Hydrographs

On the basis of these results, it is possible to compute other components of the hydrological cycle. For example, here is an illustration of the maximum velocity of baseflow, as computed by VIC.

Mekong Baseflow Maximum Velocity
Mekong Baseflow Maximum Velocity

Further, the model is capable of computing the distribution of important parameters related to agriculture, including evapotranspiration and soil moisture (illustrated here).

Mekong COVE Interface
Mekong COVE Interface

With the basic dynamics adequately described by the model, scenarios of change can be evaluated, including the impacts of landuse change and the developing sequence of dams along the Mekong (to be included here, shortly).