Water resources and salinity management in agricultural areas of inland Northern China and Northern Australia

China

Dr Ali Riasat
Phone: (08) 9333 6329
Fax: (08) 9333 6211
Email:

• Changchun Institute of Geography, Chinese Academy of Sciences, China
• Ningxia Bureau of Geology and Mineral Resources, China

$993,358

01/01/2001 - 31/12/2004

01/01/2005 - 30/09/2005

Dr Ian Willett

As a result of its extensive use of irrigation to expand agricultural activity over the last few decades, many areas of Northern China now suffer shortages of domestic and irrigation water supplies; an expansion of water-logged areas; the development of alkaline, sodic or saline soils; depletion and contamination of groundwater; increasing saline discharges to lakes and rivers; and nutrients and pollutants contaminating surface soil and water. Western Australia's Ord Bonaparte project is poised to increase its irrigated area from the current 13,000 ha to 60,000 ha. To manage such a large irrigated area sustainably, and prevent similar problems, planners will need reliable data and a good understanding of the entire catchment region.

This project is developing a holistic understanding of the surface and groundwater hydrology of three regions:
the Yinchuan Plain, in Ningxia province, where agriculture is sustained by irrigation from the Yellow River and most of the cities and villages rely on groundwater aquifers;
the Songnen Plain, in Jilin and Heilongjiang provinces, where the climate is semi-arid and agriculture relies on irrigation from the Songhua River and from groundwater; and
the Ord River Irrigation Area in Western Australia, also in a semi-arid zone and now being developed to use the water flows from the Ord Dam.

The project sought to establish the appropriate amounts of water that could be pumped from different aquifers in irrigated areas of northern China and the Ord River (WA) without depleting them or endangering water quality with salinity.

The project was divided into 10 subprojects and involved extensive training of Chinese scientists. At the sites selected and instrumented at Yinchuan and Songnen Plains and the ORIA the scientists studied the interactions between surface and groundwater hydrology; seepage from irrigation and drainage network and impacts on waterlogging, soil salinisation; irrigation techniques; surface and groundwater pollution; and groundwater abstraction and impacts on sustainability and inter-aquifer hydrology.
All new data sets and existing datasets were collated and analysed. The team then used modelling to develop a better understanding of the relationship between the surface and groundwater water systems in the study regions. Scientists concentrated on determining the mechanisms of waterlogging and quantifying groundwater discharges of salt and nutrients, so as to prepare maps of the areas most vulnerable under different management scenarios.
The final part of the project investigated the potential of new irrigation techniques (such as drip methods) to reduce salinity and waterlogging, and compared crop production under different scenarios. The scientists also used the results to determine the best location of wells and developed detailed management options to ensure long-term viability of all resources.

Using the existing and newly collected data and remote sensing, detailed digital maps of the Yinchuan Plain in China and ORIA in northern Australia were prepared showing the extent of current salinity hazard.
Chinese scientists received intensive training and have now the capacity to design, develop and conduct research experiments in surface and groundwater hydrology, salinity and drainage. They can use surface and groundwater models, salinity and geochemical models and GIS to simulate the local and regional hydrological processes. They can also construct advanced databases that can be linked to models. The outputs achieved by this project were only possible due to this training.
The project identified areas that are at higher risk of salinity and shallow groundwater level development in the Yinchuan Plain. Excessive seepage from irrigation and drainage network was found to cause the development of saline shallow water tables. Then excessive evaporation due to shallow water tables resulted in the accumulation of salts in the soil surface layers.
There is widespread pollution of groundwater from nutrients, pesticides and salts. Shallow groundwater in more than 50% of the Yinchuan Plain has been polluted. It was found that pesticides and fertilisers are the most dominant sources of pollution of surface water resources of the region. But field trials and geochemical modelling revealed that up to 50% shallow groundwater can be mixed with surface water for irrigation without any significant losses in the crop productivity. Reduction in crop yield is expected if groundwater alone is used for irrigation.
Field experiments and modelling suggested that by replacing flood irrigation with furrow irrigation about 35% of the irrigation water can be saved without sacrificing productivity. Deep open drains are effective for lowering the shallow water tables and reducing soil salinity.
Evaluation of the water resources capacity of the Yinchuan Plain for irrigation, domestic and industry uses led to reommendations that in some areas around Yinchuan city the groundwater abstraction from first confined aquifer should be reduced to avoid leakage and pollution from shallow groundwater. The surface water levels in Sand Lake should be lowered by 0.5 m to help arrest the spread of salinity in the surrounding areas.
Irrigated rice production has led to excessive sodium and other salt build up and higher pH in the shallow groundwaters of the Dongdapao area of the Songnen Plain. Here it is not feasible to mix shallow groundwater with deep groundwater (irrigation water) for irrigation of the rice fields. An efficient drainage system is strongly recommended to remove excessive surface and shallow groundwater from the Dongdapao closed depressions. Models suggested that the optimum spacing of production wells in the Dongdapao area ranges from 180 to 200 metres.
In the ORIA there is evidence of excessive recharge to the groundwater through seepage from the irrigation and drainage network and monsoonal rains. Excessive runoff from irrigation water overuse carries salts and nutrients that pollute the surface water resources of the region. Irrigation and salinity modelling suggested that up to 30% water can be saved without any sacrifice in the crop productivity and risk of salinity. Modelling suggested that the water levels in some of the water bodies should be reduced to help keep groundwater at appropriate levels. Such models also indicated the likely effectiveness of the deep drainage systems in lowering groundwater levels in those areas where they have risen closer to the soil surface.