Water use strategy improving productivity and efficiency
Technologists, researchers, farmers, regulators and irrigation scheme operators are jointly evolving a water use strategy for Canterbury. The resulting water efficiencies will benefit all New Zealanders.
The strategy is being developed to benefit all stakeholders, and to be able to be scaled up and out.
Not all irrigation decisions are made at farm level. In reality, the majority of ‘influencing factors’ often extend well beyond the farm. So how do we identify and optimize the off-farm factors that influence on-farm water use?
Getting the water - managing wants, needs and resources
To effectively manage water use you have to measure it and have the means to control it. Technology enables us to adapt four important ‘influencers’:
As a user, you want to know that water is available when you want it. At times you may irrigate unnecessarily from fear of ‘missing out’. On-farm water storage can help alleviate a real or perceived demand. But when do you need it?
Accurate and timely local weather forecasts help you decide when you need water and how much you need. But how much is legally available?
On-farm practices affect regional-scale water quality that might have provincial or national consequences. Users are increasingly encouraged to demonstrate sound irrigation and nutrient management practices to comply with their consents, and want to be confident there will be water available ‘at source’ when needed. This reduces instances of ‘just in case’ irrigations.
Irrigation scheme managers and farmers need accurate and timely water supply forecasts, informing them when there will be ‘available’ rainfall and/or river flows above the abstraction threshold. Buffering with scheme-level water storage can alleviate this.
But getting the water is only part of the story.
Retaining the water and nutrients
We need to ensure that water and water-soluble nutrients are retained in the root zone long enough to be taken up by plants. If irrigated land contains soils with poor water retention properties this will reduce the efficiency of water and nutrient use and may impact downstream water quality.
We need indicators and targets for irrigation need, leaching potential and overall growth potential; timely messaging, using media such as Smartphones, reassuring us that everything is OK, or alerting us to extremes such as root-zone dryness or leaching risk.
NIWA can now offer tools to do this.
Measuring and managing the water with NIWA’s irrigation toolbox
Together, these tools enable informed water use management decisions. Here is what you will find in the current toolbox.
Our Neon compact soil monitoring station. It enables you to decide when, and how much to irrigate. Irrimate records soil moisture, as a profile (eight depths, 100 to 800 mm) and rainfall on your farm. You can view this information in near real-time via the Internet. While good on its own, Irrimate is at its best when used with other tools, especially IrriMet, NIWA's irrigation forecasting tool.
Our local on-farm, on-line irrigation forecasting subscription service provides ‘adaptability’. It provides accurate, high-resolution forecasts of key irrigation parameters for your farm, enabling you to decide when and when not to irrigate or fertilise, helping you maximise productivity and minimise water and nutrient losses.
Compact Weather Station (CWS)
Our Neon CWS is a general purpose Tier2 weather station. As an ‘adaptability tool’ its on-farm role is to record real-time local weather data to enable local forecasting.
The CWS can be integrated with NIWA’s FarmMet weather forecasts to provide 2, 6 and 15 day forecasts of local weather, and access to seasonal and long-term climate statistics.
A excellent ‘productivity and regulation compliance’ tool for sampling nutrients in soil water. This is invaluable for estimating nutrient transport to, and leaching from the root zone. Because Lysimate is inexpensive, it enables you to employ large, wirelessly-connected soil water sampling arrays that can operate unattended for weeks.
Neon flow control systems
For large or small irrigation schemes. These maintain targeted flow rates, reliably deliver the right amount of water to the right place and record the flow data required to demonstrate consent compliance to the local council.
Our computer application that relieves you of routine irrigation water scheduling and supervisory tasks. Sentinel is ideal for large or ‘smaller-but-complex’ irrigation schemes using Neon flow control systems. It monitors and provides access to the operation of an entire scheme and ensures that you remain within your consented water allocation.
Our Android Smartphone app lets you see what your irrigation scheme is doing when you can’t be there. Stardroid and Irrigation Sentinel take the irritation out of irrigation and enable you to monitor and change flow targets when you’re mobile.
Our T-120 flume water flow measurement system (standalone or part of a Neon system) helps to reliably meet your irrigation water consent obligations and improve productivity. It facilitates measurement of open-channel flow rates.
Next steps for improving water efficiency
Overall these new tools are gaining industry acceptance, as they are applied and refined by the ‘society of stakeholders’.
At the national level, the government’s National Objectives Framework presents a ‘big-picture plan’ for managing freshwater in NZ. In consultation with the water users, councils are deciding on water use values and the attributes (with limits) that need to be managed and planned for.
At the regional level, Councils are positioning resource consents to enforce caps on nutrient discharge. There appears to be a long way to go as infrequent (usually monthly) water sampling can’t adequately characterize nitrogen status in waters.
Oxidized nitrogen (nitrate) is:
- the most widespread contaminant in groundwater
- a good environmental health indicator
- a good indicator of land-use activities
- a concern for both human health and the environment
- a potential barrier to market access with trading nations.
Yet NZ has no significant continuous nitrate data. So to some extent ‘we don’t know what we don’t know’.
But what do we know?
NIWA’s National River Water Quality Network (NRWQN), established in 1989, is New Zealand’s most comprehensive freshwater quality monitoring network. A physical water sample is taken from each of the 77 sites each month. However this isn’t frequent enough to ‘notice’ nitrate concentration changes that occur over days or weeks.
Do we need continuous nitrate monitoring?
In general, yes, though not in situations where nitrate concentration changes slowly. To remove the guesswork, NZ would benefit from progressively building a ‘nitrate monitoring network’ that could provide continuous data from carefully selected benchmark locations.
Of the five forms of nutrient that we currently measure in the NRWQN, nitrate is the only one we can conveniently measure continuously. UV absorption sensors are, by far, the best choice for nitrate monitoring in most situations.
As part of NIWA's 'Innovation in Environmental Monitoring' programme, we have purchased broad spectrum UV sensors to:
- trial at selected surface water quality benchmark sites
- complement Lysimate to research nutrient uptake of plants and leaching, in different soil types under different soil moisture conditions.
This is an important and innovative step in improving the efficiency of water usage, increasing productivity, optimizing fertilizer application and reducing nitrate contamination in waterways.