A climate change report card for water Working Technical Paper 1. Changes in groundwater levels, temperature and quality in the UK over the 20 th century: an assessment of evidence of impacts from climate change .

ion from surface water or ground water. The total annual water use data from the Defra Irrigation Survey data shows similar trends to the EA NALD data, but they do not match entirely (Figure 3). This may be partly due to the different ranges of water sources covered and businesses surveyed, the different year end dates (affecting when reservoir recharge is counted), and/or inaccurate returns from water users, but is probably mainly due to the difficulty of correcting for non-returns in both datasets. A detailed discussion of the various survey differences is given in Weatherhead et al. (1997). Analyses based on the 1995 to 2010 Irrigation Surveys data appear to show very much faster rates of decline than the ABSTAT abstraction returns; however, their statistical reliability is lower, due to the limited number of surveys. The ABSTAT trend has therefore been used for the total volume abstracted, and the Defra Irrigation Survey data used to distribute that overall trend between individual crop categories. Figure 3 Comparison of the reported total volumes (Ml) abstracted/applied between 1974 and 2010 based on EA NALD and Defra Irrigation Survey datasets. Weatherhead et al Water demand Water Report Card 8 The analysis of the irrigation survey data suggests the average depths applied (volume per unit area) have been falling slowly. There has been a underlying decline in both the area of potatoes irrigated and the water applied. The picture is statistically less clear for vegetables, but tends to suggest an overall slow increase in both areas and volumes, but possibly a short-term decline more recently. In contrast, irrigation of sugar beet, grass, cereals and orchard fruit all appear to have been in longerterm decline, but have perhaps seen recent increases. Irrigation of soft fruit (e.g. strawberries) shows a steady decline in both areas and volumes, thought this is one crop where the average depths applied have increased. These trends, particularly for the important irrigated crops, highlight quite major differences to those derived previously. They suggest that the strong upward growth until around 1990 in the total volumes of water abstracted has reversed. This at least partly reflects the increasing yield and hence decreasing cropped areas needed (particularly for potatoes and some other major irrigated crops), together with increased efficiency and better scheduling. The increasing issues relating to reduced water availability and reliability, and hence a greater appreciation of its value, are also likely to have contributed. It is noted however that these short term forecasts do not include climate change (other than any already occurring), and may therefore be a temporary trend. (ii) Medium to long term future water demand (up to 2050s) Water demand forecasts are highly sensitive to the assumed prevailing socio-economic conditions. In this study, four new EA future scenarios were used (‘Innovation’, ‘Uncontrolled Demand’, ‘Sustainable Behaviour’ and ‘Local Resilience’). These reflect updated scenarios previously developed for the EA water resource strategy (EA, 2008) termed ‘Alchemy’, ‘Jeopardy’, ‘Survivor’ and ‘Restoration’, respectively (Burdett et al., 2006). In England where irrigation is supplemental to rainfall, many crops are not irrigated, and even for irrigated crops, not all farmers irrigate. Furthermore, many farmers apply less than agronomic demand, because of equipment or water resource limitations, or as a deliberate policy to maximise profit. The methodology for estimating future changes in demand is thus more complex than for say an arid area, where demand is a function of agroclimate. For irrigated cropping, water demand therefore depends on the future area Weatherhead et al Water demand Water Report Card 9 of each crop grown, the proportion of each crop irrigated, and depth of water applied. Each of these in turn depends on agro-economic and technical conditions which will inevitably change, as well as the fundamental agronomic and agroclimatic conditions, which will themselves vary. Hence, the approach developed by Knox et al (2012) integrated spatial and temporal information relating to future changes in climate, changes in land suitability (as this influences whether a crop will be rainfed or will switch to irrigated production), and the likely changes in socio-economic conditions and agro-economic policy. These ‘externalities’ are critical because they influence the extent to which adaptation measures become economically viable, and geographically where they should be promoted. The approach involved a number of discrete stages. In 2012, a stakeholder workshop was organised to discuss the four EA scenarios and their impacts on irrigation demand. It was important to highlight any ‘givens’ – these are drivers where it was assumed that there is just one possible future development across all scenarios, or which are already pre-defined. These included (i) climate change where it was assumed that recent developments would continue without any trend breaks, broadly reflecting assumptions underpinning the “Reference Scenario” of the Office for National Statistics (ONS) in its projections for demographics and a relevant scenario from the Intergovernmental Panel on Climate Change (IPCC) for climate change and UKCP09; (ii) population demographics which were already defined under each EA scenario, (iii) consumption patterns and behaviour which were already part of the ‘axis of uncertainty’ so their status was already given in the EA scenario, and (iv) government interventions in EU and national agricultural policy which were similarly already part of the same ‘axis of uncertainty’ defined in the EA scenario. Workshop participants were asked to prioritise a set of ‘drivers for change’ that would most influence future water demand. Those given highest priority included water use and availability, price and availability of resources, including energy and land, price and availability of staple crops, land use and productivity, global demand for food products, global food markets and environmental quality and biodiversity. Two exercises were then conducted. The first involved a qualitative description of how these ‘drivers of change’ might impact on agriculture within each EA scenario. This helped to provide an agricultural narrative. The second exercise involved generating estimates of change (direction and magnitude) for five micro-components of demand (MCD), namely, national consumption, the proportion of the crop grown in the UK, yield, the cropped area and proportion irrigated. For each EA scenario, a consensus regarding the direction of change and magnitude of change for each MCD, in each sub-sector (arable, potatoes, horticulture) was then completed. The MCD outputs were then converted into numeric values, and expressed as ‘% change factors’ (either direct changes or asymptotic to either 0% or 100% for proportions, depending on the variable). These change factors were informed by a review of evidence to identify typical historical rates of change, as they could be indicative of likely future rates of change. For example, crop yields have doubled over the last 40 years, so it would be reasonable to assume that they could double (+100%) again over the next 40 years. In contrast, the future change in national consumption for a particular crop commodity (e.g. vegetables) is likely to be tied to the population growth rate so more conservative increases might be more realistic (e.g. +10 to +20%). This approach helped to weight the outputs from the scenario workshop. For each sub-sector and each EA scenario, the rates of change were mathematically combined to estimate future water use for each sub sector (Knox et al., 2012). A summary of each EA scenario and impact on future agricultural water demand is given below. ‘Innovation’ resulted in a +157% increase to the 2050s, abstracted within environmental constraints. A high technology and knowledge-led society with consumption in a relatively resource intensive Weatherhead et al Water demand Water Report Card 10 manner led to growth in potatoes (+44%), horticulture (+34%), arable (+14%) and other crops (+8%). The high demand increases for potatoes and horticultural crops is due to higher per capita consumption and population growth, but offset by substantial yield increases. The cropped areas are grown under intensive conditions managed by agribusiness with a higher proportion irrigated than at present and scheduled for high yield and quality under a more arid climate. ‘Uncontrolled demand’ represents a consumption based scenario that results in the largest increase in water demand (+167%). There is no significant change in overall food demand other than to supply the substantial population increase. Potatoes remain the largest abstractor accounting for nearly half all water use (49%); there is also major growth for vegetable irrigation (27%) and nearly a fifth (15%) for arable irrigation to meet increased population food needs. ‘Sustainable Behaviour’ resulted in a gradual steady growth in demand, rising by around +42% by the 2050s, again concentrated on potatoes (+56%) and vegetables (+27%). This scenario featured low resource consumption and local food production using greener technologies, with lower yields and less emphasis on quality assurance. Diets are more vegetable based than meat, population growth is modest but the decline in imports and lower yields results in significantly more land needed for cultivation. There is little emphasis on GM and new technologies due to the lack of past investment. There is a larger area grown under potato irrigation than at present, but mainly on family farm units rather than large scale agribusiness. Without demands for quality assurance, irrigation is widely used to boost yield. ‘Local Resilience’ resulted in a similar increase in demand to sustainable behaviour (+40%) due to population growth and climate chan