Regional water and soil assessment for managing sustainable agriculture

• Chinese Academy of Science, China

In much of the world, improving the efficiency of water use can help promote both the sustainability and the productivity of agricultural systems. There are two factors in this equation: the pressures on the existing water resource and any limitations in the efficient use of that water in agriculture. To assess water-related limitations in agriculture, and the off-farm impacts of inefficient water use, predictive models and indicators of environmental sustainability are needed, both for the farms and for the catchments in which they operate.
This study focused on four major regions of agricultural production in China and Australia, all of which had significant problems of soil and water degradation. In the Chinese study sites, agriculture was well developed but productivity without irrigation tended to be low. Soil erosion was a problem, as well as lack of available water at the right time for crops.
In the Australian sites salinisation was a problem, along with waterlogging and other land degradation problems caused by rising groundwater tables.
The project was designed to help local farmer groups and advisers identify signs of soil and water degradation, to provide information on appropriate actions to combat the problems and to monitor progress.

The project aimed to improve water-use efficiency (WUE) and reduce related land degradation in defined agricultural areas in China and Australia.

The study focused on four main regions:
the North China Plain (NCP), where soil degradation (waterlogging, salinity and sodicity) and declining groundwater levels due to inefficient water use are concerns.
the Loess Plateau, where the main problems are lack of water availability for crops and soil erosion.
the eastern part of the Mount Lofty Ranges (interchangeably called the Adelaide Hills) and the Upper Murrumbidgee catchment (both part of the Murray-Darling Basin in southeast Australia). The main problems here are salinisation, waterlogging and sodicity caused by rising saline groundwater.
The study was divided into four subprojects: the first established and validated an operational water balance model using data collected from the sites; the second subproject examined the interaction between soil salinity, plant water uptake and hydraulic conductivity; the third subproject collated the results and outcomes from the first two subprojects, while the fourth concentrated on technology transfer.
The research program involved developing guidelines and tools applicable at the local level. Scientists determined indicators of both WUE and land degradation and conveyed the findings to farmers and relevant organisations in both countries. They used and developed the integrating concept of 'water-use efficiency' to assess and rank the productivity of dryland farming systems. Indicators and computer models were also developed - where irrigation was possible, the model was developed to match timing of irrigation with crop water requirements, in order to maximise water-use efficiency and minimise the environmental hazards associated with irrigation.

Specific outputs resulting from the project were: validation in Australia and China of the WAVES model (an integrated energy and water balance model that has been under development with CSIRO and its partners since 1993), including the development of tools for optimising irrigation schedules based on increasing WUE; hillslope hydrology measurement and modelling; increased understanding of the soil-water processes linked to elements of degradation (specifically salinity and sodicity, as well as erosion on the Loess Plateau); the development of methods for the regional analysis of moisture availability, annual water yield, soil erosion, soil salinity and sodicity mapping, crop assessment and WUE mapping; refinement and application of indicator methods at farm, regional and national levels.
The research developed indicators for WUE and related land degradation, including waterlogging, salinisation and ground water recharge, in the Chinese study regions. Analogous work was conducted in catchments in South Australia and Victoria. In the irrigated parts of the North China Plain, models were developed to match the timing of irrigation with crop water requirements, with the object of maximising WUE and minimising the environmental hazards associated with irrigation.
The major outcome of the Chinese segment of the project was the consistent monitoring of agricultural WUE over 20% of the 300,000 km2 North China Plain from 1984 until 1996. Professor Liu Changming implemented the method for routine generation of maps of WUE throughout the entire Hebei Province, with funding supplied by the Hebei provincial government.
The project also prepared farm-level management manuals for both Australian and Chinese farmer groups and advisers, to help them identify signs of soil and water degradation. The project team had strong interaction with local farmer groups in both countries and with policy makers at local, State and national level.