WaterVision Agriculture: instrumentarium to quantify the effects of water management and climate on agricultural production. WaterVision Agriculture is a method to determine the impact on agricultural production of changes in hydrological conditions. These changes can be the consequence, for instance, of water management, redesign projects, (drinking) water abstraction, but also of the climate. Existing assessment systems, such as the HELP method, are based on obsolete data and do not take into account the consequences of climate change for crop yields. WaterVision Agriculture does accomplish this and can be used to determine crop loss (damage), but also to optimise water management under changing climate and other conditions, both at a regional and national scale. WaterVision Agriculture can thus contribute to achieving a climate-robust agricultural area design. Although the core of WaterVision Agriculture is based on complex processes in the soil-water-plant-atmosphere system, it is easy to apply.
Interest: translating agro-hydrological conditions into agricultural yields
The objective is to make WaterVision Agriculture the instrumentarium used by Dutch water managers in tackling questions concerning hydrological conditions and crop yields. WaterVision Agriculture can be used to determine the climate-proof relations between water management conditions and crop yields, while distinguishing between drought-, oxygen- and salt-stress. The system is intended as a replacement for the today’s commonly used systems, such as the HELP and TCGB tables, AGRICOM and Waternood. It is connected with an operational method to calculate the economic consequences for the farmer. WaterVision Agriculture is thus a tool whose applications include the calculation of the effects of water-table decisions and design plans, and the determination of the impact of groundwater abstraction on crop production. It can also provide insight into the effects of climate change under otherwise unchanged conditions (‘What happens if I do nothing?’). Agricultural organisations, Water Authorities and water utilities have long called for a review of the currently employed methods, because they are obsolete and are possibly producing inaccurate results. For instance, the determination of the effects of wet or drought damage is based on obsolete knowledge, and historical meteorological and crop data. Moreover, the HELP methodology only provides insight into long-term average effects. Salt damage is not, or is only to a limited extent, processed in the models. Most of all, the existing models are not suited to incorporating the consequences of an increasingly capricious climate in the calculations. With WaterVision Agriculture, the most up-to-date state of knowledge is operationalised in a model instrumentarium and in a practical application tool. This tool makes it possible to translate changes in water management and possibly climate change into crop yield and losses.
Approach: from science to practice
To assess the consequences of climate and/or water management changes on the functioning of plants, one needs to explicitly consider the essential processes that describe the interaction between soil, water, plant and the atmosphere. This process knowledge is then operationalised and tested against practice data. For the most common agricultural crops, the direct effects are determined in WaterVision Agriculture by simulations with the hydrological model for the unsaturated zone of SWAP (Soil-Water-Atmosphere-Plant), coupled with the dynamic crop-growth model WOFOST (WOrld FOod Studies). For other crops, SWAP’s simple crop model is used. The soil conditions with regard to drought, oxygen availability and salt concentration determine whether transpiration reduction and crop losses will occur. We call these the direct effects. WaterVision Agriculture also takes into account the indirect effects, such as postponed seeding and harvest times due to limited soil workability under wet conditions, or delayed crop growth in the event of cold spring conditions. For the economic calculations, a connection was made with the BBPR [BedrijfsBegrotingsProgramma Rundvee (Cattle Operational Budget Programme)], for dairy farming, and the KWIN database, for arable farming and field vegetables. In order to bypass simulations with the complex modelling tools SWAP-WOFOST in the application of WaterVision Agriculture, the relations between groundwater properties, soil types and yields are derived on the basis of a large number of detailed SWAP-WOFOST simulations. In this way, the results of the detailed process models can be easily applied via so-called ‘meta-relations’. These can be simply and quickly applied as post-processing of the results of a groundwater model, at both regional and national scale. The meta-relations are derived for the five KNMI main stations (current climate: 1981-2010), the KNMI climate scenario WH, and the 72 soil physical map units (BOFEK2012) in the Netherlands. With the procedures for the derivation of meta-relations, one can also derive, for a specific area with a more detailed soil description, tailored meta-relations.
Results: WaterVision Agriculture – practical applicable tools
With the available SWAP-WOFOST simulation models (http://swap.wur.nl), the users can also themselves calculate specific situations (in both space and time) or have them calculated – for example, if they want to analyse in detail the impact of extreme weather events on the yield of a specific crop. However, special expertise is needed to conduct tailored calculations with SWAP-WOFOST. Moreover, SWAP-WOFOST is applied at a land-parcel scale and the model instrumentarium is less suited for spatial analyses. However, the derived meta-relations significantly facilitate the translation of hydrological conditions into crop yields for spatial analyses. Groundwater levels are directly translated via the meta-relations into yield losses. The meta-relations, collected in the WWL table, provide both the long-term average loss percentages for different crops, as well as the results for one specific year – a dry or a wet year for example. WaterVision Agriculture prototypes were used in a few pilot applications, and the lessons learned were incorporated into the further development of the model instrumentarium. A wide support base was created under the auspices of STOWA for the development of WaterVision Agriculture, and a consortium of a large number of stakeholders collaborated on the project. In this way, a considerable support base was created to promote the implementation of WaterVision Agriculture. The aim is to have WaterVision Agriculture applied, for instance, by the Water Authorities, provinces, Advisory Commission for Damage related to Groundwater (ACSG), Rijkswaterstaat, consultancies and (indirectly) by the Ministries of Agriculture, Nature and Food Quality and of Infrastructure and Water Management, as well as the Delta Programme Freshwater Plan. The model instrumentarium can be applied by different users to tackle different questions with different objectives, but the relation between hydrological conditions and agricultural production remains central. WaterVision Agriculture is designed in such a way that new insights, process knowledge and improvement wishes can be built in. It can therefore always provide an updated and properly performing model instrumentarium. WaterVision Agriculture is freely available via http://www.waterwijzer.nl/.