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This report, an output from the UKRI-funded Drought and Water Scarcity Programme, synthesis the insights for the agricultural sector. It considers how drought and water scarcity affect different types of agriculture; whether we can forecast drought and its impacts and how drought and water scarcity impacts on agriculture be reduced?

This report, an output from the UKRI-funded Drought and Water Scarcity Programme, synthesis the insights for the agricultural sector. It considers how drought and water scarcity affect different types of agriculture; whether we can forecast drought and its impacts and how drought and water scarcity impacts on agriculture be reduced?

Supporting information for paper from Anglian Water funded Water Resources East project

This report is part of the "Land use, climate change & water availability (Phase 2a)" project which was commissioned and funded by the Department for Environment, Food and Rural Affairs (Defra). It provides an initial quantification of the effects of changes in land use and land management on average annual Hydrological Effective Rainfall (AAHER) and Potential Baseflow uising a soil water balance model (WaSim). The effects were considered in present and future climates by using the FutureFlows climate change ensemble. The changes modelled were informed by the plausible future land use and management changes (induced by climate or social change by the 2050s) identified in the literature review in Task B - in particular regarding changes in land use (e.g., changes in agricultural and forest areas) and changes in cropping calendars and sowing/harvest dates.

This report is part of the "Land use, climate change & water availability (Phase 2a)" project which was commissioned and funded by the Department for Environment, Food and Rural Affairs (Defra). Based on a review of the literature, it describes plausible characteristics of future land use and management changes (induced by climate or social change by the 2050s) that are likely to influence water availability.

Water saving in agriculture often refers to reducing the amount of water abstracted or diverted and used for different purposes. However, this is not the only option: reductions in water use can also be achieved by using appropriate techniques for irrigation, applying relevant management practices, using water from alternative sources or influencing behaviour – for example, via awareness-raising, dissemination of best practices, regulation, water pricing and/or the use of financial incentives. While these options or responses will help to reduce pressure on water resources, if implemented in isolation they limit the extent to which water is actually ‘saved’. More often, they need to be considered as part of a broader integrated approach to water management. This paper presents a framework for identifying areas in which scope for achieving water savings exists and then reviews the possible means of action and the constraints to implementation. The framework is intended to inform polices aimed at improving the sustainability and allocation of water to irrigated agriculture. http://www.ippublishing.com

Developed by HR Wallingford and Cranfield University (with support from the UK Department for International Development), WaSim is a computer-based training package for the teaching and demonstration of issues involved in irrigation, drainage and salinity management. WaSim is a daily water balance model that simulates the soil water / salinity relationships in response to different management strategies (e.g. drainage designs and water management practices) and environmental scenarios (e.g. weather data, soil types, cropping patterns).

Current accepted tools in risk assessment include techniques such as Fault and Event Tree analysis to predict the level of safety risk. To date, use of these tools at Grade Crossings has been limited and analysis has reverted to safety performance statistics to correlate results. There has been a missing link in modeling to be able to provide meaningful estimates of safety risk. Until now practitioners have been unable to use factors such as sighting, conspicuity, train speed, and human behavior characteristics within their numerical techniques. Working for Network Rail, the Railway operation company in the United Kingdom (UK) Halcrow has been using theoretical techniques to quantify safety risk at grade crossings. During this work we have applied a new tool in modeling safety risk, the Event Window. Using this concept, we have been able to relate variables such as sighting, user perception and predict human error against a timeline. The nearer a moving train to a grade crossing the less likely a user will cross in error. The advantage of this technique is that it takes into account the one common factor in past accidents, how users incorrectly judge train speed. In this paper we shall address the following questions: 􀂃 What is the benefit of quantifying the safety risk at a grade crossing? 􀂃 How do these risk assessments help organizations responsible for risk at grade crossings discharge their duties? 􀂃 What is the quality or usefulness of different types of evidence in building up these models? 􀂃 How can we improve on existing risk assessment techniques to make more informed and location specific decisions on grade crossing safety? 􀂃 How does the Event Window assist us in predicting safety risk? Tim Hess, AIMechE, Halcrow Group Ltd Jim Haile BSc CEng MIMechE, Halcrow Group Ltd

Concerns about increased flood risk and loss of biodiversity in lowland areas, coupled with changing priorities in the countryside have drawn attention to the potential contribution that managed washlands can make to improved flood management, habitats and wildlife. Following a review of research literature, a survey of flood managers and conservation officers, and an evaluation of selected case sites in England, a framework to help integrate potential flood management and biodiversity opportunities was constructed. This framework consists of three components, namely: a Hydraulic classification which categorises washlands according to degree of hydraulic control; a Habitat classification which captures attributes of washland hydrology that define the type of existing or potential habitats; and, a Menu of Interventions to “engineer” or manage particular flooding and soil wetness regimes and thereby better exploit habitat potential. Washlands were also categorised by main type of benefit whether this is flood management, conservation, or in the case of integratedwashland, a balance of the two. The advantages of alternative administrative and funding arrangements for washlands, whether land acquisition or annual payment to existing land owners, were also explored. It was concluded that the classification of washland flooding and water level regimes can help to define habitat potential. It can also help to guide hydraulic engineering and management actions that can be taken to realise this potential. Although there is potential synergy between flooding and biodiversity under some flood regimes, biodiversity benefits mainly depend on the management of water regimes following flood events. There is a clear need to “join up” hitherto fragmente

In the context of growing interest in finding sustainable solutions to flood management in England and Wales, this study set out to determine the extent to which benefits to flood management and biodiversity can be achieved through an integrated approach to the creation and management of ‘washlands’. For the purpose of the study, a washland is defined as “an area of the floodplain that is allowed to flood or is deliberately flooded by a river or stream for flood management purposes, with potential to form a wetland habitat”. Following a questionnaire survey of engineers and conservationists, a review of selected sites, and a workshop of key stakeholders, it was concluded that there is both scope and willingness to exploit potential synergy. It appears, however, that until now most washlands have either been used mainly for flood storage or for wetland habitat, and there has been only a limited attempt to integrate the two objectives. In many respects, the opportunity for integrating biodiversity depends on the ability to maintain wet conditions on the washland beyond the period of the flood event, and this largely depends on the dominant land use. The scope is greatest where the washland is under grass or woodland, and actions can be taken to ‘engineer’ or manage soil wetness regimes which serve biodiversity interests. Such water management plans and related biodiversity targets are best designed into washland management from the outset, rather than as an afterthought, when conflicts of interest are likely to arise. While there is much interest in pursuing an integrated approach, lack of funding for biodiversity on washlands and the relative complexity of preparing the washland case for appraisal appear to constrain washland development. Nevertheless, washlands are perceived by engineers and conservationists alike to offer potentially sustainable solutions to flooding, enabling biodiversity targets to be met within an integrated approach to catchment flood management. Recommendations were made to: • improve, through the use of guidance and training, understanding between engineers and conservationists of how flood management and biodiversity objectives can be simultaneously achieved; • consider the establishment of a biodiversity fund to support the biodiversity components of washland schemes; • develop practical guidance on the formulation of washland management plans that exploit biodiversity potential by managing wetness conditions in washlands beyond the flood-event period; • review how washland creation and management can be integrated and help to deliver the objectives of Biodiversity Action Plans and Catchment Flo

1) MAFF has recently launched a scheme to support the expansion of the area of energy crops grown in England in order to meet the nation’s Kyoto targets for the reduction in CO2 emissions. This has highlighted concerns about the possible effects of willow short rotation coppice (SRC) and Miscanthus on the hydrology of catchments in which they are grown. High levels of water use by these crops could result in less surface runoff, decreased aquifer recharge and hence reduced stream flow (Chapter 1

Irrigation constitutes a major user of water resources at a time, and in places, where resources are at their lowest. Also, by maintaining the soil in a wetter state, it increases the annual drainage, which can affect the leaching of nitrates into the groundwater. Irrigation scheduling involves, firstly, deciding the most appropriate irrigation plan (i.e. what soil water deficit to allow and how much to apply at that deficit) and secondly, deciding what is the soil water deficit on any particular day. Good scheduling will aim to meet the goals of irrigation (optimise production / quality / aesthetics) whilst minimising the water used and other adverse environmental impacts. The main techniques for scheduling irrigation in the UK are direct measurement of soil water content and water balance modelling. ‘Bad’ irrigation scheduling can result from an inappropriate irrigation plan, inaccurate soil water measurement, errors in water balance modelling or uncertainty over the actual amount of water applied at each irrigation. Either will result in under- or over-watering. A case study for potatoes grown in a medium textured soil in Silsoe (Beds) examined the impact of poor scheduling on average annual irrigation water requirement and the risk of nitrate leaching. The water requirement is very sensitive to errors in estimating evapotranspiration or the field-capacity water content of the soil, but less so to errors in the amount of water applied. Increasing the trigger soil water deficit can also minimise the water requirement. Over-irrigation, due to a poor irrigation plan can increase the summer drainage and risk of nitrate leaching, however, over-watering due to inaccurate scheduling predominantly results in increased winter drainage which may have a positive impact on nitrate concentrations and winter recha

The study confirmed that water use for agricultural irrigation is increasing, both in area irrigated and depths applied, and is increasingly concentrated on the more valuable crops. Underlying volumetric growth was 3% per annum from 1982 to 1995. On-farm reservoir capacity doubled from 1990 to 1995, but 90% of the water still came from summer abstraction in 1995, mostly from rivers and streams.

This paper compares the use of different methods for estimating reference evapotranspiration (ETo) for irrigation scheduling in the UK. Methods include use of long-term averages, daily weather data and evaporimeters. The results from a single trial in Silsoe in 1996 suggest that, with careful maintenance and measurement, a modified atmometer such as the ETgage, can give estimates of ETo which are close to those obtained using the Penman-Monteith equation.

Water limitations typically reduce UK wheat yields on average by 1-2 t ha- 1 , although this can be considerably more in extreme drought years. With the frequency and intensity of droughts expected to increase under a changing climate, an improved understanding of the impacts of drought and better systems for agricultural drought monitoring are required. Previous studies, however, have found no significant relationship between UK wheat yields and commonly employed drought severity indices (DSI). Using historical (1911-2015) daily weather data for Cambridge the Standardized Precipitation Index (SPI), the Standardized Precipitation and Evapotranspiration Index (SPEI), the Palmer Drought Severity Index (PDSI) and the Potential Soil Moisture Deficit (PSMD) were calculated on various time steps (e.g. 1-12 months for SPI and SPEI) to provide a drought record for the site. A wheat crop growth simulation model (Sirius) was then used to simulate the effects of the identified historic droughts on wheat yields. The use of the Sirius crop model removed the non-drought related yield losses (e.g. disease, pests, and lodging) present in national yield records. Using the Spearman’s Rho correlation coefficient (r) the simulated yield record was then correlated against the different DSIs. The droughts of 1921, 1976 and 2010 were found to be the most extreme in term of yield reduction. In addition, there were also two noticeable periods of successive yield loss in the early 1940s and between 2009 and 2013. All DSIs showed significant (p = 0.05) correlations on monthly time steps between April and August. The SPI, SPEI and PSMD showed a strong correlation to wheat yields (r = 0.64 to 0.66) on time steps incorporating the end of the ‘construction’ and the entirety of the ‘production’ phases for wheat growth. The PDSI showed the weakest correlation (r = 0.55), although it may be helpful in identifying yield-limiting droughts earlier in the year. The research has contributed new scientific insights and understanding of the impacts of historic droughts on wheat productivity, and demonstrated the application of DSIs in monitoring potentially yield-limiting droughts. The research also provides new evidence to support developments in UK food security and drought management for agriculture.

There is a regulatory tension within wastewater treatment, between the requirement to meet tightening consents and the need to reduce the carbon footprint of treatment processes. With 75% of wastewater treatment works serving populations of less than 2,000, low-energy tertiary treatment options suitable to small rural works need to be developed. One option that lends itself particularly well to small works is land-based wastewater treatment (LBWWT). The aim of this research was to evaluate the role of LBWWT in the UK water industry and investigate the impact ridge-and-furrow enhanced microtopography (MT) may have upon a particular type of LBWWT - slow-rate (SR) infiltration. This was achieved through meeting three objectives. Firstly, the use of LBWWT was reviewed and assessed. Secondly, the impact of ridge-and-furrow enhanced MT upon the vegetation diversity and nutrient removal of a SR- LBWWT was established by means of a three year field trial. Finally, the cost- effectiveness of SR-LBWWT and the impact of ridging and furrow irrigation upon cost-effectiveness were evaluated using Cost-Effectiveness Analysis (CEA). The first objective comprised of a review of the historical and current use of LBWWT, a review of the relevant changing legislation to identify what may be required of LBWWT and an assessment of LBWWT’s potential to meet these requirements. The result of the evaluation found that, based upon the literature, SR-LBWWT is ‘fit-for-purpose’ as tertiary treatment for small treatment works. To meet the second objective, a SR-LBWWT system trial was established at a small wastewater treatment works in Knowle, Hampshire. The trial consisted of three clay-loam grass plots irrigated with secondary treated effluent. There were two configurations of trial plot - flat and ridge-and-furrowed. Effluent (sub- surface soil water) nutrient concentrations were monitored as was vegetation diversity. In addition a number of physical, hydrological and biogeochemical parameters were monitored and hydrological modelling carried out. Mean nutrient removal performances of 90% for ammonia, 72% for nitrate, and 91% for phosphate were observed with the ridge-and-furrowed plot. Ridging and furrow irrigation was found to not have a significantly detrimental effect upon the trial plots’ removal performance for ammonia, nitrate or phosphate. Extrapolation modelling suggested, however, that this would not be the case for LBWWT systems on predominantly clay or sand soils. Ridging and furrow irrigation was found to have a statistically significant positive effect upon the vegetation diversity of the LBWWT trial plots; with mean final year Shannon-Wiener values of 0.96 and 0.69, for the ridge-and-furrowed and non-ridged plots, respectively. For the final objective, analysis found that SR-LBWWT are cost-effective when compared to horizontal sub-surface flow constructed wetlands (HSSFCW), an established low-energy treatment option. Mean cost-effectiveness ratio values of £208.5 and £262.7 per % effectiveness were observed for LBWWT and HSSFCW, respectively. Following the field trial CEA was extended to include ridge-and-furrowed SR-LBWWT systems. This found that ridging and furrow irrigation improves the cost-effectiveness of SR-LBWWT serving small populations, reducing the mid cost-effectiveness ratio to £193 per % effectiveness. This is a result of the cost-reducing effect of ridge-and-furrowing over laser-level grading; and based upon the findings of the trial that ridging and furrow irrigation can be achieved (in clay-loam soil slow-rate systems) without significant detriment to the water treatment effectiveness of LBWWT. The main conclusions of this thesis are: that SR-LBWWT has a role to play in the UK water industry, as tertiary treatment for small wastewater treatment works. That SR-LBWWT is cost-effective in relation to HSSFCW. That ridging and furrow irrigation increases that cost-effectiveness by reducing the construction and operational costs. That ridging and furrow irrigation can be employed without significant detriment to a SR-LBWWT system’s water treatment performance. And finally, that ridging and furrow irrigation can have a positive impact upon the establishment vegetation diversity of a SR-LBWWT system.

Seven UK fields located across Oxfordshire, Southampton and W. Berkshire, five cropped in winter wheat in 2014 and two in 2013 were investigated to assess the effect of soil variability on mean yield and yield variance under flat-rate and variable- rate nitrogen applications. The high level aim being to provide information to help guide growers on how best to apply nitrogen fertiliser to increase yield and enhance yield uniformity. Data layers were collated for shallow Electrical-Conductivity (EC), Leaf Area Index, nitrogen application and yield. Yields were neither significantly higher under flat-rate nor variable-rate treatment (p = 0.8356). Variation in shallow EC was neither significantly more different in the variable-rate treatments or the flat- rate treatments (p = 0.7862). Variability in EC held a positive relationship with yield variability under both flat-rate (R2 = 0.2102) (p = 0.0213) and variable-rate treatment (R2 = 0.1507) (p = 0.0176). This suggests that variable-rate treatment provided no significant benefit in reducing yield variability.

Floodplains in the United Kingdom have evolved from natural landscapes to artificially modified ecosystems through managing lateral and vertical floodplain connectivity leading to synergy or trade-offs in ecosystem service delivery. Research methods have been limited in understanding the processes by which ecosystem service values are formed and the data required to support ecosystem service assessment. Developing a methodology while complex and challenging is necessary in order to take the ecosystem approach forward to support decision making for policy makers, planners and stakeholders. The aim of this research was to develop a method to assess the delivery of ecosystem services in response to changes in floodplain connectivity and evaluate the performance. A case study floodplain was selected at Tempsford, downstream of the River Ivel in Bedfordshire, United Kingdom as an example for opportunities to deliver multiple ecosystem services. A sequential integrated modelling system was applied utilising a linked ISIS 1D-2D hydrodynamic model and WaSim, a 1D soil water balance model to simulate changes in floodplain connectivity and generate model data to improve estimates of ecosystem services indicators. A non- monetary multi-criteria analysis methodology was applied to further develop indicators for ecosystem services assessment and to assess the impacts of the model scenarios on ecosystem services delivery. The integration of the WaSim model was unsuccessful as the model performed poorly in the calibration and validation process and was not fit for its intended purpose. It was deduced that potential groundwater seepage in the regional aquifer occurs outside of the field study site, which cannot be modelled in WaSim. To demonstrate the impact of lateral connectivity controls on the water table position, an empirical method was developed using the mean observed water table position to represent a ‘no drainage system’ vertical connectivity scenario. The results showed that in low frequency/high magnitude flood events, increasing the lateral connectivity by lowering embankments provides synergy and benefits to flood alleviation, water supply and freshwater fish habitat and trade-offs and disbenefits to flood damage, agricultural productivity, terrestrial habitat and recreation. In high frequency/low magnitude flood events, decreasing the lateral connectivity by raising embankments still provides the same synergy and trade-offs yet lower benefits and disbenefits. Marginally decreasing the lateral connectivity creates a higher level of benefits and a lower level of disbenefits to promote multi-functional land use in the floodplain. Managing the control of floodplain connectivity needs to be carefully planned to enable multifunctional land use in a floodplain.

Globally, onion (Allium cepa L.) represents an extremely important crop in terms of production, value and consumption. Similarly, in the UK onion production is considered to be one of the most important high-value field vegetables, with ca. 300,900 tonnes being produced from 8,448 ha (DEFRA 2010). However, a great variability in onion productivity (yield) has been identified due to a combination of environmental, genotypic, management and agronomic factors. The increasing demand for high quality vegetables and their supply year round is adding significant pressure on farming enterprises, which add to the challenges UK onion producers already face (e.g. crop management, irrigation and pest control decision-making). The aim of this research was to assess the impacts of in-field soil and irrigation variability on onion yield and quality. Therefore, the scientific evidence on the relationships between onion yield, crop water use, irrigation and crop quality were initially reviewed and the evidence corroborated with data from an industry survey. In order to evaluate the effects of soils and irrigation variability on yield, under different agroclimatic conditions, a crop growth model (AquaCrop) was calibrated and then validated using experimental field data. The scientific evidence in the literature and results from the industry survey were used to validate and calibrate the AquaCrop model for brown onion (cv Arthur). Statistical analyses were used to assess crop model goodness of fit. A series of scenario were then defined and the AquaCrop model used to assess the impacts of different onion cropping practices, production areas and typical and extreme climatic conditions on crop yield. The effects of irrigation non-uniformity (typical of a boom and linear move irrigation application system) on production were assessed under a series of agroclimatic conditions (five different years) and two contrasting soil types (sandy and sandy loam). The simulations showed that the lowest yield (8.6 t DM/ha) and greatest variability (standard deviation: 0.23 t DM/ha) occurred under the driest agroclimatic conditions. Production on sandy soils resulted in higher yield (in average 0.24t DM/ha) than on a sandy loam soil. The yield under hosereels fitted with booms were statistically significant (Kruskal-Wallis analysis) lower than for the linear move, although the difference was very small (average of 9.52 t DM/ha vs. 9.56 t DM/ha). Under ‘average dry’ conditions, the highest yield was produced on sandy soils (8.78 t DM/ha), contrary to ‘average’ agroclimatic conditions, where the highest yield was produced on sandy loam soils (9.55 t DM/ha). For the driest season, the effects of irrigation variability were only significant on sandy soils (8.80 t DM/ha and 8.73 t DM/ha for hosereel fitted with linear move and boom, respectively). The study of uniform versus non-uniform irrigation applications showed that onion yield was higher under uniform irrigation. The differences between yields produced under uniform and non-uniform irrigation increased with increasing climatic aridity (0.01-0.18 t DM/ha compared to average values). Differences were greater in cases of boom application systems. Onion yield generated by simulations of uniform conditions fell within the range found in the literature. The variability observed under non-uniform irrigation was the same (up to 30-40%) as the overall variation reported by growers.