EcoHouse Research

Vaishnavi Balachandran (MEng, 2013)

 

 

Global water resources are facing increasing pressure from rapidly growing population, economic growth, water pollution, land-use changes and climate change. The uncertain future of growing demand and external factors such as climate change provide a continuing challenge for the management of water resources to balance environmental and developmental needs. The future uncertainty has led to increasing interests in modelling of water resources particularly at a river-basin level.

 

The challenges facing policy-makers from competition for limited resources require adaptation strategies that take into account the trade-offs and concerns of different stakeholders. Several hydrological models are available for a wide range of applications. However, many of them require large data inputs and time to run often making them impractical for use as decision tools. There is a need to develop simple practical tools that enable water resource managers to better collaborate with stakeholders in decision-making processes to understand the outcomes of various management strategies under future uncertainties.

 

This project develops a simple catchment-scale water balance and quality model that can be used as a collaborative tool between multiple stakeholders. The model is applied to the Mekong River Basin in South-East Asia. The Mekong is facing several challenges as a result of rapid population growth and economic development. In particular, hydropower development throughout the basin and increasing irrigation demand for agriculture coupled with climate change are causing rapid changes that will affect future land and water resources. These could have significant consequences for the basin population who rely on these resources threatening livelihoods and food security in the basin.

 

The model is based on the long-term water balance concept combined with the rational method to calculate annual and seasonal runoff, which were calibrated against runoff data. The water quality is based on the mass balance concept for calculating the chemical loading in the runoff, using the calibrated flows from the hydrology model. These were calibrated and validated with water quality data for Chemical Oxygen Demand, Nitrates and Total Suspended Solids. The Chemical Oxygen Demand and Total Suspended Solids models were further improved by applying an exponential decay equation.

 

A water quality index (WQI) was developed based on international drinking water standards. The WQI provides a simple method of conveying water quality information in a concise manner. Whilst the WQI means some of the quality model preciseness is lost, it has its advantages in representing the data in a simple manner allowing comparisons to be made readily. This is particularly important in using the WQI for decision-making purposes. It can easily be adapted for other water uses and purposes.

 

The project explores how the model can be used to consider various possible scenarios in the Mekong affecting water flows and water quality, including climate and land use changes and hydropower development. The hydropower scenarios demonstrate how the tool could be used by multiple stakeholders to communicate their perspectives of the impacts of the development on them. This was explored through the use of hypothetical WQIs, adapting the WQI for drinking water quality, to reflect the views of a few key stakeholders including subsistence farmers, local fishermen and hydroelectric engineers. These were based on evidence and opinions about the likely impacts of the dams on total suspended solids in the water and the consequences of the development on each stakeholder. This could allow them to collaborate in dialogue over the trade-offs required to achieve equitable and sustainable resource allocation.

 

The simplicity of the model structure with few parameters and limited data requirements allows the model to be readily calibrated. The nature of the calibration process and given the sparse data requirements means that more than one calibration is possible, with different combination parameters giving slightly different yet still valid calibrations. It was demonstrated how the final calibration can be influenced by the modellers’ personal views and opinions and therefore vary between different users. The basic model structure means that it could be transferred to other study areas and be used to explore water quantity and quality issues. The model’s simplicity means that it cannot provide precise results or answer specific questions about the catchment. However, it could be useful as a collaborative tool in decision-making processes to facilitate stakeholder participation in understanding the full impacts of the possible uncertainties and risks and to plan more informed future management strategies to minimise them.