USCID fourth international conference

Presented at the Role of irrigation and drainage in a sustainable future: USCID fourth international conference on irrigation and drainage on October 3-6, 2007 in Sacramento, California.Includes bibliographical references.A In order to promote irrigation sustainability through reporting by irrigation water managers around Australia, we have developed an adaptive framework and methodology for improved triple-bottom-line reporting. The Irrigation Sustainability Assessment Framework (ISAF) was developed to provide a comprehensive framework for irrigation sustainability assessment and integrated triple-bottom-line reporting, and is structured to promote voluntary application of this framework across the irrigation industry, with monitoring, assessment and feedback into future planning, in a continual learning process. Used in this manner the framework serves not only as a "reporting tool", but also as a "planning tool" for introducing innovative technology and as a "processes implementation tool" for enhanced adoption of new scientific research findings across the irrigation industry. The ISAF was applied in case studies to selected rural irrigation sector organisations, with modifications to meet their specific interests and future planning

Evaluating a multi-level subsurface drainage system for improved drainage water quality

This paper describes a multi-level drainage system, designed to improve drainage water quality. Results are presented from a field scale land reclamation experiment implemented in the Murrumbidgee Irrigation Area of New South Wales, Australia. A traditional single level drainage system and a multi-level drainage system were compared in the experiment in an irrigated field setting. The single level drainage system consisted of 1.8 m deep drains at 20 m spacing. This configuration is typical of subsurface drainage system design used in the area. The multi-level drainage system consisted of shallow closely spaced drains (3.3 m spacing at 0.75 m depth) underlain by deeper widely spaced drains (20 m spacing at 1.8 m depth). Data on drainage flows and salinity, water table regime and soil salinity were collected over a 2-year period. Comparisons of water and solute movement between the multi-level drainage system and a single level drainage system are presented. Differences in the performance of the multi-level and single level drainage systems were found in the water table regime, drain water salinity and soil salinity

Soil Spatial Variability Effects on Irrigation Efficiency

Higher evapotranspiration rates, reduced rainfall and increased water scarcity have led to a need for improved irrigation water use efficiency. Evaporation is a significant component of the total evapotranspiration (ET) and high evaporation losses reduce the amount of available water for transpiration, resulting in reduced plant water availability and hence increased irrigation. Values for soil evaporation vary widely in the literature, from 27-65% of total ET. In order to increase transpiration relative to evaporation, a reduction in evaporative losses is needed. Spatial variability of evaporation is an important factor that needs to be taken into consideration when improving water use efficiency. Soil physical properties control evaporation by influencing both the transport of water toward the soil or root surface and soil water storage. The effect of variability in soil properties on evaporation is likely to be larger in cases with water deficiency. Cultural practices such as use of narrow row spacing, mulch and minimum tillage can reduce evaporation however, they are not always effective. The potential for major savings of water depends on the length of drying interval following irrigation or rain. There is the potential for reductions in evaporation losses of up to 60% through the use of improved management techniques, enabling more water to be used by the plant for transpiration. In order to improve water use, more research in quantifying evaporation variability at the field scale needs to be completed

Controlled water table management as a strategy for reducing salt loads from subsurface drainage under perennial agriculture in semi-arid Australia

Recent community based actions to ensure the sustainability of irrigation and protection of associated ecosystems in the Murrumbidgee Irrigation Area (MIA) of Australia has seen the implementation of a regional Land and Water Management Plan. This aims to improve land and water management within the irrigation area and minimise downstream impacts associated with irrigation. One of the plan objectives is to decrease current salt loads generated from subsurface drainage in perennial horticulture within the area from 20 000 tonnes/year to 17 000 tonnes/year. In order to meet such objectives Controlled Water table Management (CWM) is being investigated as a possible ‘Best Management Practice’, to reduce drainage volumes and salt loads. During 2000–2002 a trial was conducted on a 15 ha subsurface drained vineyard. This compared a traditional unmanaged subsurface drainage system with a controlled drainage system utilizing weirs to maintain water tables and changes in irrigation scheduling to maximize the potential crop use of a shallow water table. Drainage volumes, salt loads and water table elevations throughout the field were monitored to investigate the effects of controlled drainage on drain flows and salt loads. Results from the experiment showed that controlled drainage significantly reduced drainage volumes and salt loads compared to unmanaged systems. However, there were marked increases in soil salinity which will need to be carefully monitored and managed

Using a mobile phone Short Messaging Service (SMS) for irrigation scheduling in Australia - Farmers' participation and utility evaluation

Irrigation scheduling Decision Support Systems (DSS) have seen poor uptake despite proved usage benefits. The failures of some previous systems with proven model accuracy and water savings ability have been attributed to interface difficulties and inappropriate information for end users. Use of the mobile phone Short Messaging Service (SMS) text messages was trialed as an interface to overcome these difficulties. Irrigation system dripper run time scheduling advice was sent daily to 72 Australian irrigators' mobile phones from a water balance system called IrriSat SMS. Irrigators sent back information on irrigations and rainfall, also via SMS, to update the water balance. This trial showed that a complex, water balance-based, DSS could rely on SMS as the sole interface. All 72 irrigators involved were content to receive messages daily for the entire growing season (200 days). A measure of engagement and utility of the system was determined by those who returned their irrigation and rainfall data, 45 sent in their data all season, 13 for half the season and 14 never sent in any data. Thus we infer that 45 users (63%) found the SMS system of enough utility to use for the whole season. Also, at end of season, 6 of the 13 who had stopped half way through said that in retrospect they wished they had not. Thus overall 80% of irrigators found the system useful. User interview data showed the simplicity of use, advice and the prompting effects of intrusive delivery (phone ringing) were key features in the resultant strong engagement of irrigators. Success also relied on appreciating that irrigators will only use objective decision support advice as one element in a set of decision making tools that include subjective and unquantifiable elements, such as plant appearance. This strong uptake reverses the trend in irrigation decision support which has seen poor uptake of sophisticated systems that produce comprehensive scheduling support but which are, or are perceived to be, complex and time consuming to use. Additionally, high participation rates show that much model input data may be collected from irrigators via SMS so it can be used as a very cheap bi-directional communication channel

Estimation of soil evaporation in an irrigated vineyard from soil surface temperature

Soil evaporation is a significant unproductive loss of water that needs to be and can be managed in irrigated systems. A method is used to estimate soil evaporation based upon soil surface temperature change between a saturated and drying soil. The relative evaporation (RE) method of Ben-Asher et al. (1983) was deployed. Soil surface temperature in a drip irrigated vineyard was collected using infra-red temperature sensors. Average daily soil evaporation under-vine was between 0.6mm and 1.8mm and between 0.7mm and 2.5mm for the inter-row. Evaporation from the soil is an important part of the water balance of a crop (Burt et al. 2005). Previous estimates vary widely, from 30-65% of evapotranspiration (Kerridge et al 2008a). The Ben-Asher et al. (1983) method allows potential soil evaporation to be estimated from the daily latent fluxes of a saturated, steady-state dry and a drying soil. By calculating a relative evaporation (RE) factor and multiplying it by an estimate of potential evaporation, determined for example by the FAO-56 procedure (Allen et al., 1998), an estimate of soil evaporation may be made. The main benefit of this method is that it allows rapid and simultaneous estimates of evaporative flux to be measured at numerous sites under study. This can then be linked with methods for spatial estimation of plant water use and stress (Hornbuckle et al., 2008b)

Modelling the Fate of Molinate in Rice Paddies of South Eastern Australia Using RICEWG

Contamination of drainage channels and creeks with pesticides used in rice production is of concern in south eastern Australia. Of major concern is the herbicide molinate that is detected in over 25% of water samples. This pesticide has been the focus of researchers and environmental protection authorities due to continuing frequent detection off farm despite improved application methods and water management guidelines. The objective of this study was to assess the rice pesticide model RICEWQ version 1.7.2 for its applicability in simulating pesticide in runoff in south eastern Australia. The model was successfully calibrated against field data on water depths and molinate concentrations from a rice field in the Murrumbidgee Irrigation Area. It was found that the calibrated model was able to simulate the field data in the supply bay adequately; however it is not capable of modelling rice fields with multiple bays, which are much more complex than a single bay situation. Sensitivity analyses of the parameter values on molinate concentrations in ponded water, sediment and foliage were performed. Overall the application efficiency has a major impact and this impact is carried throughout the entire simulation. In ponded water the bulk density, mixing velocity, release rate for slow release formulation, pesticide solubility and water/sediment partition coefficient were relatively sensitive. In the sediment the release rate and the mixing , soil bulk density, degradation rate in the sediment, water/sediment partition coefficient and mixing velocity have large sensitivities. On the foliage only three parameters have non-zero sensitivities, the application efficiency, the wash off coefficient and the degradation rate on foliage. The calibrated model was used to investigate water and pesticide management for a single bay. It was found that water management was critical to minimising molinate runoff. Using a 41 year weather sequence for Griffith in the Murrumbidgee Irrigation Area it was found that if water levels were maintained 5 cm below the drainage outlet there was little likelihood of surface runoff occurring. Simulation of the registered label application methods and rates for molinate were undertaken. These compared application onto a dry bay, a ponded bay and application by ground rig, aerial, and Soluble Chemical Water Injection In Rice Technique (SCWIIRT) low pressure system. The greatest maximum concentrations of molinate in the ponded water occurred when molinate was applied directly onto the water. The maximum concentrations for application onto a dry bay were an order of magnitude lower than for the applications onto a bay filled with water. However, the pesticide concentrations in water declined more rapidly for the application onto a water filled bay than for application onto a dry bay. Field trials are required to assess the accuracy of these results as no data comparing ponded water and dry bay applications is available. The comparison of application methods was undertaken by adjusting the application efficiency parameter. This ranged from 60 % (assumed) for the aerial application on dry bay, to 70 % (assumed) for the ground rig, 95 % for aerial application, determined from the model calibration, and 100 % (assumed) for the SCWIIRT. The results showed that increasing the application rate by 60 % increased the period during which the water molinate concentration was above guideline level by 11 %. The results indicate that the application amount is only critical to the concentration of molinate in runoff if it occurs in about 30 days after application. The results regarding molinate concentrations in water with time and effects of different application rates suggest that poor application efficiency results in a major loss of chemical. If the application efficiency could be improved and application aimed at a target concentration then lower application rates of molinate could potentially be as effective as current label rates. This requires further research

Triple bottom line reporting to promote sustainability of irrigation in Australia

Irrigation development induces considerable environmental change, but the expectation has been in the past that the economic and social benefits would be greater than the environmental costs. However, public attitudes change over time from acceptance of development and exploitation to greater concern regarding environmental issues and sustainability. Recently, the irrigation industry has found it difficult to communicate to the wider populace the regional benefits of irrigation and the current activities and investment undertaken to address the environmental sustainability concerns. To address this, irrigation water supply businesses are investigating using a broader reporting structure that includes financial, environmental, and social and cultural elements. This triple bottom line, holistic approach should provide a more balanced view of water use with socio-economic benefits and environmental consequences demonstrated. It is anticipated that this approach embedded in the newly developed Irrigation Sustainability Assessment Framework will lead to a more transparent and informed debate on the sustainable use of resources between all parties