Quantitative analysis techniques have gained a great deal of popularity with decision-makers and analysts in recent years, this is also the case in hydrology. Since conjunctive water use for agriculture is turning out to be a major environmental challenge in some river basins, there is an urgent need to quantify the future water availability and water demand to identify whether there is a surplus or deficit of water. This is of great importance in developing water management plans for a basin or a state. In this paper, the Basinwide Holistic Integrated Water Assessment (BHIWA) model developed by International Commission on Irrigation and drainage (ICID) was used in an attempt to simulate the water balance of the study basin, Qiantang River Basin in China, as well as to analyse the impacts of land and water use on return flows of this basin. Four water situation indicators were propounded in the model to depict the level of water use (withdrawals) and potential risks (due to return flows) to water quality. Stochastic analysis was also done in this paper using Monte Carlo Simulation Method, by randomly selecting sets of values for the probability distributions in the cell values and formulas to quantify the risks in terms of water quantity and water quality resulting from climate change and return flow. "Quantifying risk" means determining all the possible values a risky variable could take and determining the relative likelihood of each value. BHIWA can be used to simulate and analyse the impacts of land use and climate change on water resources and eventually optimize the water allocations among agricultural, industrial, domestic, and environmental sectors within a basin context. A decision support tool called @RISK has been used to perform stochastic analysis on water supply and water demand. This allows the relationship between the reliability of the supply system and the capacity of its storage tank(s) to be quantified using Monte Carlo analysis. There are two basic approaches to quantitative risk analysis.They are simulation and analytical approach. Both have the same goal — to derive a probabilitydistribution that describes the possible outcomes of an uncertain situation — and both generate valid results. A major strength of @RISK is that it allows users to work in a familiar and standard model building environment — Microsoft Excel. Variables are the basic elements in the Excel worksheets that have been identified as important ingredients to the analysis. @RISK uses probability distributions to describe uncertain variables in Excel worksheets and to present results. The estimated water budgets simulated from BHIWA model were in general in good agreement with the estimated water balance by the provincial water conservancy department. The model provided reasonable estimates for current water recharge to groundwater and potential for the sustainable development of surface and groundwater as well as export of water from the basin. However, the surface water withdrawals for irrigation are relatively high, ranking from 2,903 million cubic meters to 6,523 million cubic meters with 90% of probability. Therefore, expansion of irrigation infrastructure and improvement of soil and water management measures should be adopted to increase the efficient use of irrigation water. In addition, the contamination threat to the groundwater is significantly high due to high proportion of return flow to groundwater (varying from 0.18 to 0.58); this might result in poor groundwater quality in future. Given the water situation in the basin, the model amply demonstrates the scope for enhancing the present storage and regulation capacity of water resources. Besides a possible opportunity for interbasin transfer of water from Qiantang basin to other water short areas also came to light.
|Title of host publication||Land, Water and Environmental Management|
|Subtitle of host publication||Integrated Systems for Sustainability|
|Editors||Les Oxley, Don Kulasiri|
|Place of Publication||Christchurch, New Zealand|
|Publisher||Modelling and Simulation Society of Australia and New Zealand|
|Number of pages||7|
|Publication status||Published - 2007|
|Event||International Congress on Modelling and Simulation (MODSIM) - Christchurch, New Zealand|
Duration: 10 Dec 2007 → 13 Dec 2007
|Conference||International Congress on Modelling and Simulation (MODSIM)|
|Period||10/12/07 → 13/12/07|
Mu, J., & Khan, S. (2007). Stochastic Analysis of Water Supply and Demand at the River Basin Level. In L. Oxley, & D. Kulasiri (Eds.), Land, Water and Environmental Management: Integrated Systems for Sustainability (pp. 184-190). Modelling and Simulation Society of Australia and New Zealand.