FAQs

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No. We are acutely aware of the sensitivity of business data we are asking you to input to D-Risk. Therefore, the tool is implemented such that no data are stored in the D-Risk computer server once you close the webtool.

Whilst this means that you will have to re-enter your data when you re-visit D-Risk, we have made data entry as quick and easy as possible.

If you would like further information on our Data Protection and Confidentiality policies at Cranfield University then please get in touch.

To avoid excessive data entry, D-Risk assumes that the irrigated crop mix and areas each year remain constant. However, you can easily use D-Risk to see how sensitive your licensed headroom and irrigation deficits are to changing crop types and irrigated areas.

Yes, the crops available to choose in D-Risk represent the most common commercial crops for which established relationships between agroclimate and theoretical crop irrigation needs have been developed drawing on previous work by Cranfield University. If you want to assess irrigation requirements for a crop that is not within the list, or a specific variety (e.g. pre-pack potato), then you can choose a crop from the list with similar planting and harvesting dates and modify the “irrigation correction factor” to match your estimated irrigation needs for that crop. For example, if you want to represent turnip, then you can select parsnip and modify the irrigation correction factor to reduce or increase the crop water requirements according to your farm experience.

The analyses within D-Risk rely on specific farm level data provided by the user which are then combined with gridded weather data that are representative of the area including the farm postcode. However, given that every drought event is different and that droughts are infrequent, the weather dataset used in D-Risk needs to also include a wide range of potential drought events, in order to develop a risk-based approach to assessing drought impacts on irrigated production.

D-Risk therefore uses a recently released gridded weather dataset called the ‘MaRIUS event set’ which contains 100 time series of equally probable weather, each of 30 years length. This dataset has been verified against long-term observed weather data from the Meteorological Office The postcode for the farm site is used to extract the relevant weather data for the grid square in which the farm is located. We have used the MaRIUS event set data in two ways:

  • Firstly, we have assumed that the future probability or likelihood of a given level of irrigation need is based on all of these time series and years - this is equivalent to basing the probability of rolling a given number on a dice on 3000 (100 x 30) throws of the dice. We have termed this analysis as ‘average’ conditions;
  • Secondly, we have assumed that the future probability or likelihood of irrigation need is based on the years in a single time series - this is equivalent to basing the probability of rolling a given number on a dice on just 30 throws of the dice. In this analysis, some of these time series will be drier (or have a greater number of extremely dry years) than others. These ‘driest’ and ‘wettest’ time series then provide an uncertainty boundary (envelope) around the long term ‘average’.

The estimation of theoretical crop irrigation needs in D-Risk is based on previous research carried out by Cranfield University. This research was used by the EA in support of their abstraction licence renewal process to assess what they term “reasonable needs”.

Knox et al. (1996, 2007) derived a set of relationships between annual irrigation need and agroclimate for the range of crops and soil types included within D-Risk. These relationships are implemented in D-Risk, with the annual agroclimate calculated from the weather data for the grid square in which your postcode is located. From these data, and using the relationship corresponding to each combination of crop and soil selected, D-Risk then calculates annual series of theoretical irrigation need. This is the ‘net’ annual need and excludes any additional water that might be needed to account for irrigation system inefficiency.

Readers interested in how these relationships were developed are referred to:

Knox, J. W., Weatherhead, E. K., & Bradley, R. I. (1996). Mapping the spatial distribution of volumetric irrigation water requirements for maincrop potatoes in England and Wales. Agricultural Water Management, 31(1-2), 1-15.

Knox, J. W., Weatherhead, K., & Ioris, A. A. (2007). Assessing water requirements for irrigated agriculture in Scotland. Water International, 32(1), 133-144.

Morris, J., Weatherhead, E. K., Mills, J., Dunderdale, J.A.L., Hess, T., Gowing, D.J.G., Sanders, D., & Knox J.W. (1997) Spray irrigation cost benefit study. Cranfield University.

The current version of D-Risk assumes that there are no abstraction constraints or restrictions (other than defined within the licence conditions). This means that the results of D-Risk can be interpreted as the ‘best-case’ on top of which the possible effects of voluntary or mandatory abstraction restrictions should be added.

You could develop a better understanding of the effects of different levels of potential restrictions by reducing your daily licence limit, the effect of which will be greatest in the driest years in which restrictions are most likely.

At licence renewal, you are usually expected to justify ‘reasonable need’ based on the combination of crops you grow, the areas of each that are irrigated and the soil types on which those crops are grown, as well as the application methods you use. D-Risk can therefore be used to help quantify the ‘reasonable needs’ (depths applied, mm) for your farm taking into account current crop mixes and by combining with the irrigated areas (ha) estimate volumetric irrigation demand (m3). The D-Risk data relates to a ‘design’ dry year, so you can then use this data to compare this theoretical volume against how much you actually abstracted in a recent dry year. You will also need to add in an additional factor to account for net and gross irrigation demand, i.e. how much extra you may have used to account for system inefficiencies. The D-Risk data should be helpful in giving you an indication of how much you could theoretically irrigate with your licence against how much you actually irrigated. If you would like to seek further professional advice, please contact us at enquiries@d-risk.eu

You can use D-Risk to explore how adding new or additional reservoir storage capacity would affect your ‘risk profile’. For example, if you already have a reservoir and storage licence, you can simply re-run D-Risk with a modified total storage capacity. If you do not have a reservoir, you will need to specify the reservoir capacity and either define a new storage licence for your farm (as reservoirs cannot be filled using a licence specified for ‘spray irrigation -direct) or convert part of your direct abstraction licence/s to storage.

We recommend you to carry out this process several times or iterations to find the storage capacity and storage licence requirements that best address your drought risk. If you would like to seek further professional advice, please contact us at enquiries@d-risk.eu

Each grower and business has a unique tolerance of drought risk, so there is no set probability (or risk) threshold that you can use. You should select a probability that has associated deficit and headroom results with which you feel comfortable- however, it is common to use the 5th driest year in 20 (or the 80th percentile probability of non-exceedance) in designing new irrigation infrastructure. You must take into account that the lower you want your risk to be, the higher the level of investment you will require. Also, remember that while risks can be minimised, they cannot be completely eliminated.

D-Risk uses the specified daily licence limit to limit peak irrigation usage. In this case, whilst the annual licence volume is sufficient to meet the volumetric demand over the year, the daily licence limit is insufficient to meet peak irrigation demand in the summer.

If you are interested in further advice regarding your D-Risk outputs, or you are interested in performing more detailed analysis of your business, please contact us at enquiries@d-risk.eu