A critical comparison of using a probabilistic weather generator versus a change factor approach: irrigation reservoir planning under climate change

In the UK, there is a growing interest in constructing on-farm irrigation reservoirs, however deciding the optimum reservoir capacity is not simple. There are two distinct approaches to generating the future daily weather datasets needed to calculate future irrigation need. The change factor approach perturbs the observed record using monthly change factors derived from downscaled climate models. This assumes that whilst the climate changes, the day-to-day climate variability itself is stationary. Problems may arise where the instrumental record is insufficient or particularly suspect. Alternatively, probabilistic weather generators can be used to identify options which are considered more robust to climate change uncertainty because they consider non-stationary climate variability. This paper explores the difference between using the change factor approach and a probabilistic weather generator for informing farm reservoir design at three sites in the UK. Decision outcomes obtained using the current normal practice of 80% probability of non-exceedance rule and simple economic optimisations are also compared. Decision outcomes obtained using the change factor approach and probabilistic weather generators are significantly different; whether these differences translate to real-world differences is discussed. This study also found that using the 80% probability of non-exceedance rule could potentially result in maladaptation

Irrigation demand modelling using the UKCP09 weather generator: lessons learned

The determination of irrigation demand is typically based on crop modelling using a long historic record of local daily weather data. However, there are rarely adequate weather station records near to given sites; often any local records cover a limited number of years, are incomplete, costly or are of poor quality. This paper examines whether version 1 of the UKCP09 weather generator can provide a simpler and effective method of calculating irrigation demand with sufficient accuracy for regulatory and design purposes. The irrigation demands at seven sites distributed around England were modelled using the UKCP09 baseline climatology and compared with results modelled using daily observed weather records. For the design dry year used for irrigation planning, the weather generator replicated the observed conditions with reasonable accuracy. The weather generator was however less successful at replicating extreme dry years. These results are encouraging but also provide a note of caution for the use of these generated datasets for studying current irrigation demand and by implication for modelling future needs under climate change. The study also demonstrated a simple sub-sampling approach for reducing the processing demands if using the dataset in more complex models, though this would not remove any underlying error

Assessing spectral similarities between rainfed and irrigated croplands in a humid environment for irrigated land mapping

Deriving accurate spatial assessments of the distribution of irrigated crops has become more important in recent years for water resource planning, particularly where irrigation water resources are constrained. However, this is easier in arid climates than in humid areas such as eastern England. The challenges in using alternative vegetation indices derived from remote sensing to discriminate between irrigated and rainfed crops in a humid climate are described, focusing on potato (Solanum tuberosum L.), the most important irrigated crop in England. Three techniques were evaluated: (a) temporal profile comparisons using the Normalized Difference Vegetation Index (NDVI); (b) cluster analysis combining the NDVI and the Normalized Difference Water Index (NDWI); and (c) identifying differences in chlorophyll content using green and near infrared bands. However, the study confirmed that the spectral signatures of irrigated and rainfed potato in England during a typical summer are very similar, presumably due to frequent rainfall events which reduce differences in water stress and chlorophyll content. The implications for using remote sensing to estimate irrigated areas in humid climates are discussed

Power-Sharing in the English Lowlands? The Political Economy of Farmer Participation and Cooperation in Water Governance

Participatory and cooperative forms of water governance have become regular features of government discourse and stated policy objectives in England. We consider this aspiration from the perspective of farmers in the English lowlands, by analysing the current power dynamic that exists among these farmers, and between them and the key stakeholders involved in water management. To do this we undertake a political economy analysis that places lowland farming and water governance within the evolution of historical processes that, over time, have influenced the ability of farmers to participate in the governance of their water environment. These historical developments are interpreted through the lens of the Power Cube, an analytical tool for thinking about the interplay between different forms of power operating in different types of spaces and at different levels of governance. Our findings reveal that, despite there being a number of structural changes that provide lowland farmers with the opportunity to participate and cooperate in water governance, three distinct barriers stand in the way. These relate to the power 'within' these farmers, which continues to align with a productivist ideology founded on individualism and competition, often at the expense of the environment; the power that government water managers still exercise 'over' farmers instead of 'with' them; and the relationship between lowland farming and environmental interests, where historically the two sides’ power 'to' act has been diametrically opposed. The findings point to the importance of developing suitable programmes designed to support and incentivize farmer participation and cooperation

Climate change impacts on water for irrigated horticulture in the Vale of Evesham. Final Report

This project has undertaken a scoping review and assessment of the impacts of climate change on irrigated horticulture in the Vale of Evesham, an area of intense irrigated production located within the Environment Agency’s Warwickshire Avon CAMS Catchment. The research was based on a combination of methodologies including desk-based review of published and grey literature, computer agroclimatic and water balance modelling, GIS mapping, meetings with key informants and a stakeholder workshop. Future climate datasets were derived from the latest UK Climate Impacts Programme (UKICIP02) climatology, using selected emission scenarios for the 2020s, 2050s and 2080s. These scenarios were then used to model and map the future agroclimatic conditions under which agriculture might operate and the consequent impacts on irrigation need (depths of water applied) and volumetric demand. This was complimented by a postal survey to abstractors and a stakeholder workshop, to identify, review and assess farmer adaptation options and responses. The key findings arising from the research, implications for water resource management and recommendations for further work are summarised below. Using a geographical information system (GIS), a series of agroclimate maps have been produced, for the baseline and selected UKCIP02 scenario. The maps show major changes in agroclimate within the catchment over the next 50 years. The driest agroclimate zones are currently located around Worcester, Evesham, Tewkesbury and Gloucester, corresponding to areas where horticultural production and irrigation demand are most concentrated. By the 2020s, all agroclimate zones are predicted to increase in aridity. By the 2050s the entire catchment is predicted to have a drier agroclimate than is currently experienced anywhere in the driest parts of the catchment. This will have major impacts on the pattern of land use and irrigation water demand. Cont/d

Competition, Conflict, and Compromise: Three Discourses Used by Irrigators in England and Their Implications for the CoManagement of Water Resources

In this paper we use discourse analysis to explore the current dynamic that exists among farmer irrigators in England, and between irrigators and water managers in order to understand the potential for co-management to develop. To do this we employ two concepts from the field of critical discursive psychology – 'interpretive repertoires' and 'subject positions' – and apply them to a qualitative analysis of 20 interviews with farmers who are members of irrigator groups and two focus group discussions with farmers thinking about forming an irrigator group. The findings reveal that the participants drew upon three interpretive repertoires when talking about the relationship between farming and water resources management, namely the 'competition', 'conflict', and 'compromise' repertoires, with the latter being the least dominant. We situate the repertoires in their wider historical context to reveal the ideological forces at play, and conclude that the relative dominance of the competition and conflict repertoires serve as a barrier to co-management. In particular, this is because they engender low levels of trust and reinforce a power dynamic that favours individualism and opposition. At the same time, the less-dominant compromise repertoire challenges the power of the other two, providing some hope of achieving more participatory forms of water resources management in the future. To this end, we discuss how the restructuring of current agri-environment schemes and government water programmes may be used to promote the adoption and institutionalisation of the compromise repertoire in order to facilitate the emergence of co-management

The economics of irrigating wheat in a humid climate - A study in the East of England

In the UK, wheat is the most important cultivated cereal, grown extensively as a rainfed crop. Irrigation of wheat has previously been considered uneconomic, but increases in world wheat prices and recent droughts have led to some farmers revising their views. Widespread adoption of wheat irrigation would have major implications for wheat production, the irrigation industry and water resources in regions that are already water scarce. This study investigated the financial viability of irrigating winter wheat grown on a sandy loam soil in the East of England. Long-term climate data (1961–2011) for Silsoe (Bedfordshire) was used to drive a biophysical crop model to assess irrigation water requirements and yield response. Modelling assumed a typical irrigation schedule to maximise yield and quality, and average reported wheat prices for 2007 to 2012. Irrigation costs were calculated assuming an overhead mobile hosereel–raingun system applying river water, abstracted either in summer and used directly, or abstracted in winter and stored in an on-farm reservoir. The results suggest that the yield benefit would justify supplemental irrigation by farmers who have unused irrigation equipment and unused summer water, although irrigation of higher-value field vegetable crops later in the season would normally take precedence – the Added Value of Water (AVW) usefully applied to milling winter wheat under these conditions ranged between 0.24 and 0.32 £ m−3. Investment in new irrigation schemes could also be marginally viable if unused summer river water was available for direct abstraction (AVW = 0.08 £ m−3). Investments in new farm reservoirs for irrigating wheat are currently not profitable (AVW = –0.23 £ m−3). Sensitivity analysis suggests that in the longer term, the expected increase in world wheat prices and the impacts of climate change are likely to make the financial benefits stronger, particularly in the drier catchments further east and on low moisture retentive soils, but competing demands for water would still make extensive wheat irrigation unlikely

Difficulties in using spectral properties to map irrigated areas in a temperate climate: A case study of potatoes in England

Irrigation in England is supplemental to rainfall and only used on a small proportion of the cultivated land, notably on high value vegetable and potato crops. However, it is a significant water user as most of the irrigated area is located in the driest part of England. The existing data on irrigated areas are based on government and industry surveys. Recently these datasets have been used with Geographic Information Systems (GIS) to produce irrigated maps, but these can only be published at catchment level due to confidentiality constraints on the datasets. To assess the possibility of using remote sensing data for mapping the irrigated area, one Landsat image for the summer 2003 was used to compare the spectral signature between irrigated and non-irrigated potato fields in the East of England. ISODATA algorithm was used to perform unsupervised classification, and 50 spectral classes were created. A ground truth dataset was then used to identify the most representative spectral class for irrigated and nonirrigated fields. The result showed that categories both fall into the same spectral class, suggesting there are no significant differences between their spectral properties. Therefore, using satellite imagery may not yet be an appropriate method or need more research for mapping irrigated area in temperate climates such as England. The summer rainfall reduces the water stress differences between irrigated and non-irrigated potato fields such that these satellite sensors cannot yet differentiate the crops

Using the politicized institutional analysis and development framework to analyze (adaptive) comanagement: farming and water resources in England

The challenge of managing water resources in England is becoming increasingly complex and uncertain, a situation reflected in many countries around the world. Cooperative and participatory forms of governance are now seen as one way of addressing this challenge. We investigated this assertion by focusing on five farmer irrigator groups in the low-lying east of England. The groups’ relationship with water resources management was interpreted through the lens of comanagement, which over the past decade has increasingly merged with the field of adaptive management and related concepts that derive from resilience thinking and complex adaptive systems theory. Working within a critical realist paradigm, our analysis was guided by the politicized institutional analysis and development (IAD) framework. Two previous studies concerned with the broader context surrounding farming and water governance in lowland England revealed low levels of trust between farmers, and between farmers and water managers, as well as a power dynamic that stands in the way of farmer cooperation and participation. Within this context, our findings pointed to a number of mechanisms and structural conditions that appear to generate or facilitate comanagement. Of these, institution building through the specific group strategy of adopting a company structure and the “stationarity” of the resource group members extract from were seen to be the most crucial. These and other key findings were used to inform a discussion of farming and water resources management in England going forward. In doing so, we also reflected on the relationship between comanagement and market-based approaches to managing water resources. Beyond this, the research serves as a practical demonstration of how the politicized IAD framework can be used to analyze potential (adaptive) comanagement situations and the related benefits. The analysis complements a previous submission to this journal, in which we discussed the relationship between the framework and (adaptive) comanagement from a theoretical and methodological perspective

An Integrated Approach to Analyzing (Adaptive) Comanagement Using the "Politicized" IAD Framework

Scholars of comanagement are faced with a difficult methodological challenge. As comanagement has evolved and diversified it has increasingly merged with the field of adaptive management and related concepts that derive from resilience thinking and complex adaptive systems theory. In addition to earlier considerations of power sharing, institution building, and trust, the adaptive turn in comanagement has brought attention to the process of social learning and a focus on concepts such as scale, self-organization, and system trajectory. At the same time, a number of scholars are calling for a more integrated approach to studying (adaptive) comanagement that is able to situate these normative concepts within a critical understanding of how context and power fundamentally influences the behavior of a system. We propose that the “politicized” version of the Institutional Analysis and Development (IAD) Framework, originally developed by Elinor Ostrom and her colleagues, is well suited to addressing this challenge. The framework provides breadth, clarity, and structure by drawing the analyst’s attention to the range of variables and questions to be considered when attempting a study of comanagement, the various components of the situation, and the ways in which they interact, and the criteria the analyst may wish to adopt in evaluating the outcomes of the process. Alongside its ability to address contextual factors and power dynamics, the socioeconomic and institutional dimension of the politicized IAD Framework means that it can be used to conduct analyses that result in sound policy recommendations