Mac Kirby

Economic Assessment of Acquiring Water for Environmental Flows in the Murray Basin

This article is an economic analysis of reallocating River Murray Basin water from agriculture to the environment with and without the possibility of interregional water trade. Acquiring environmental flows as an equal percentage of water allocations from all irrigation regions in the Basin is estimated to reduce returns to irrigation. When the same volume of water is taken from selected low-value regions only, the net revenue reduction is less. In all scenarios considered, net revenue gains from freeing trade are estimated to outweigh the negative revenue effects of reallocating water for environmental flows. The model accounts for how stochastic weather affects market water demand, supply and requirements for environmental flows. Net irrigation revenue is estimated to be

Impacts of climate change on lower Murray irrigation

75 million less than the baseline level for a scenario involving reallocating a constant volume of water for the environment in both wet and dry years. For a more realistic scenario involving more water for the environment in wet and less in dry years, estimated net revenue loss is reduced by 48 per cent to

Simultaneous X-ray imaging of plant root growth and water uptake in thin-slab systems

39 million. Finally, the external salinity-related costs of water trading are estimated at around

Adaptation to climate change for food security in the lower Mekong Basin

1 million per annum, a quite modest amount compared to the direct irrigation benefits of trade.

Impact of climate change on rainfed rice and options for adaptation in the lower Mekong Basin

This article evaluates irrigated agriculture sector response and resultant economic impacts of climate change for a part of the Murray Darling Basin in Australia. A water balance model is used to predict reduced basin inflows for mild, moderate and severe climate change scenarios involving 1, 2 and 4°C warming, and predict 13, 38 and 63% reduced inflows. Impact on irrigated agricultural production and profitability are estimated with a mathematical programming model using a two-stage approach that simultaneously estimates short and long-run adjustments. The model accounts for a range of adaptive responses including: deficit irrigation, temporarily following of some areas, permanently reducing the irrigated area and changing the mix of crops. The results suggest that relatively low cost adaptation strategies are available for a moderate reduction in water availability and thus costs of such a reduction are likely to be relatively small. In more severe climate change scenarios greater costs are estimated. Adaptations predicted include a reduction in total area irrigated and investments in efficient irrigation. A shift away from perennial to annual crops is also predicted as the latter can be managed more profitably when water allocations in some years are very low.

The Mekong: a diverse basin facing the tensions of development.

Direct and simultaneous observation of root growth and plant water uptake is difficult because soils are opaque. X-ray imaging techniques such as projection radiography or Computer Tomography (CT) offer a partial alternative to such limitations. Nevertheless, there is a trade-off between resolution, large field-of-view and 3-dimensionality: With the current state of the technology, it is possible to have any two. In this study, we used X-ray transmission through thin-slab systems to monitor transient saturation fields that develop around roots as plants grow. Although restricted to 2-dimensions, this approach offers a large field-of-view together with high spatial and dynamic resolutions. To illustrate the potential of this technology, we grew peas in 1 cm thick containers filled with soil and imaged them at regular intervals. The dynamics of both the root growth and the water content field that developed around the roots could be conveniently monitored. Compared to other techniques such as X-ray CT, our system is relatively inexpensive and easy to implement. It can potentially be applied to study many agronomic problems, such as issues related to the impact of soil constraints (physical, chemical or biological) on root development.

Water and agricultural productivity in the Lower Mekong Basin: trends and future prospects.

Variability in water cycles driven by climate change is considered likely to impact rice production in the near future. Rice is the main staple food for the population in the lower Mekong Basin and the demand for food is expected to grow due to increase in population. This paper examines the impact of climate change on rice production in the lower Mekong Basin, evaluates some widely used adaptation options, and analyses their implications for overall food security by 2050. Climate change data used in the study are the future climate projection for two IPCC SRES scenarios, A2 and B2, based on ECHAM4 General Circulation Model downscaled to the Mekong region using the PRECIS (Providing Regional Climates for Impact Studies) system. In general, the results suggest that yield of rainfed rice may increase significantly in the upper part of the basin in Laos and Thailand and may decrease in the lower part of the basin in Cambodia and Vietnam. Irrigated rice may not be affected by climate change if increased irrigation requirements are met. Negative impact on the yield of rainfed rice can be offset and net increase in yield can be achieved by applying widely used adaptation options such as changing planting date, supplementary irrigation and increased fertilizer input. Analysis of the projected production, considering population growth by 2050, suggests that food security of the basin is unlikely to be threatened by the increased population and climate change, excluding extreme events such as sea level rise and cyclones.

Agricultural productivity in the lower Mekong Basin: trends and future prospects for food security

We assessed the potential impact of climate change on the yield of rainfed rice in the lower Mekong Basin and evaluated some adaptation options, using a crop growth simulation model. Future climate projections are based on IPCC SRES A2 and B2 scenarios as simulated by ECHAM4 global climate model downscaled for the Mekong Basin using the PRECIS system. We divided the basin into 14 agro-climatic zones and selected a sub-catchment within each zone for the model and assessed the impact for the period of 2010–2030 and 2030–2050. In general, the results suggest that yield of rainfed rice may increase significantly in the upper part of the basin in Laos and Thailand and may decrease in the lower part of the basin in Cambodia and Vietnam. The increase is higher during 2030–2050 compared to the period of 2010–2030 for A2 scenario. For B2 scenario, yield increase is higher during 2010–2030. The impact is mainly due to the change in rainfall and CO2 concentration in the atmosphere. We have tested widely used adaptation options such as changing planting date, supplementary irrigation, and reduction in fertility stress and found that negative impact on yield can be offset and net increase in yield can be achieved.

Irrigator and Environmental Water Management Adaptation to Climate Change and Water Reallocation in the Murray–Darling Basin

Population is growing in the relatively unregulated Mekong River basin, and demands for hydropower and food are increasing. The basin has prospered but the poorest have not shared the benefits. Agricultural production is keeping up with rising food demand, but capture fisheries are unlikely to increase production, threatening the supply of animal protein in peoples diets. National governments decide water issues unilaterally, with weak transnational institutions and limited public participation. Growing pressures, exacerbated by climate change, will likely increase tensions over access to water, reinforcing perceptions of institutional failure and stimulating demands for improved governance.

Drought and Climate Change in the Murray-Darling Basin: A Hydrological Perspective

Agricultural productivity varies markedly across the Lower Mekong Basin. Production of rice is increasing everywhere, whereas per capita increases are marked in Vietnam and modest elsewhere. Fisheries are a major source of animal protein in all parts of the basin, especially in Cambodia and Vietnam. Production of capture fishery is static with some signs of overfishing, whereas aquaculture production in the delta is increasing rapidly. The increased population in 2050, together with changed diets, will require considerable increases in production. This requirement may be met by increasing the area under production, or by increasing the area under irrigation (with consequent downstream impacts). Production of capture fisheries is unlikely to increase, whereas aquaculture and mixed use rice–fish systems appear capable of greatly increased production. The anticipated changes to climate and hence flow are expected to affect agriculture and food production, and may make it more difficult to meet the increased food demand.