This study provides an overview on the impacts of climate change on agricultural water management, including agricultural water requirement, water availability and water quality, and the transition of those impacts to crop yield, agricultural land suitability and livestock production systems, considering both long‐term trends of climate and extreme climatic events. A synthesis of findings from local, regional, and global studies guides this article's discussion of scientifically based information, implications for managing the risk of water scarcity and food insecurity, and future research. Negative and positive climate change impacts occurring at the local scale may counteract each other at the global scale (e.g., those on irrigation requirement and arable land availability); the impacts from the various factors can be counter‐balanced too (e.g., CO2 and water deficit impact on crop yield). Meanwhile, the shocks at the local and regional levels have been or will be caused by water quantity and quality problems and are pressing concerns for decision making. Although uncertainty in climate change predictions remains a critical issue for decision making, certain knowledge about the impact on crop production has been obtained from historical data. Finally, future research needs to focus on gaining a more detailed understanding of climate change (especially extreme events), climate change impacts, both natural and social response mechanisms, and adaptation measures of agricultural water management. More focus should be laid on improving impact assessment via the various methods such as retrospective analysis, monitoring, prediction, and strategic risk management. Moreover, planned adaptations in agricultural water management will be needed to facilitate more consistent and more effective responses to climate change, with consideration of the linkage with nonagricultural water uses. WIREs Water 2015, 2:439–455. doi: 10.1002/wat2.1089 This article is categorized under: Engineering Water > Planning Water Science of Water > Water and Environmental Change

Restoration of degraded wet meadows found on upland valley floors has been proposed to achieve a range of ecological benefits, including augmenting late‐season streamflow. There are, however, few field and modelling studies documenting hydrologic changes following restoration that can be used to validate this expectation, and published changes in groundwater levels and streamflow following restoration are inconclusive. Here, we assess the streamflow benefit that can be obtained by wet‐meadow restoration using a physically based quantitative analysis. This framework employs a 1‐dimensional linearized Boussinesq equation with a superimposed solution for changes in storage due to groundwater upwelling and evapotranspiration, calculated explicitly using the White method. The model and assumptions gave rise to predictions in good agreement with field data from the Middle Fork John Day watershed in Oregon, USA. While raising channel beds can increase total water storage via increases in water table elevation in upland valley bottoms, the contributions of both lateral and longitudinal drainage from restored floodplains to late‐summer streamflow were found to be undetectably small, while losses in streamflow due to greater transpiration, lower hydraulic gradients, and less laterally drainable pore volume were likely to be substantial. Although late‐summer streamflow increases should not be expected as a direct result of wet‐meadow restoration, these approaches offer benefits for improving the quality and health of riparian and meadow vegetation that would warrant considering such measures, even at the cost of increased water demand and reduced streamflow.

Subdivision of catchment into appropriate hydrological units is essential to represent rainfall-runoff processes in hydrological modelling. The commonest units used for this purpose are hillslopes (e.g. Fan and Bras, 1998; Troch et al., 2003). Hillslope width functions can therefore be utilised as one-dimensional representation of threedimensional landscapes by introducing profile curvatures and plan shapes. An algorithm was developed to delineate and extract hillslopes and hillslope width functions by introducing a new approach to calculate an average profile curvature and plan shape. This allows the algorithm to be independent of digital elevation model resolution and to associate hillslopes to nine elementary landscapes according to Dikau (1989). This algortihm was tested on two flat and steep catchments of the province of Quebec, Canada. Results showed great area coverage for hillslope width function over individual hillslopes and entire watershed.

Subdivision of catchment into appropriate hydrological units is essential to represent rainfall-runoff processes in hydrological modelling. The commonest units used for this purpose are hillslopes (e.g. Fan and Bras, 1998; Troch et al., 2003). Hillslope width functions can therefore be utilised as one-dimensional representation of three-dimensional landscapes by introducing profile curvatures and plan shapes. An algorithm was developed to delineate and extract hillslopes and hillslope width functions by introducing a new approach to calculate an average profile curvature and plan shape. This allows the algorithm to be independent of digital elevation model resolution and to associate hillslopes to nine elementary landscapes according to Dikau (1989). This algortihm was tested on two flat and steep catchments of the province of Quebec, Canada. Results showed great area coverage for hillslope width function over individual hillslopes and entire watershed