Abstract
Droughts can exert significant pressure on regional water resources resulting in abstraction constraints for irrigated agriculture with consequences for productivity and revenue. While water trading can support more efficient water allocation, high transactional costs and delays in approvals often restrict its wider uptake among users. Collaborative water sharing is an alternative approach to formal water trading that has received much less regulatory and industry attention. This study assessed how the potential benefits of water sharing to reduce water resources risks in agriculture are affected by both drought severity and the spatial scale of water-sharing agreements. The research focused on an intensively farmed lowland catchment in Eastern England, a known hot-spot for irrigation intensity and recurrent abstraction pressures. The benefits of water sharing were modelled at four spatial scales: (i) individual licence (with no water sharing), (ii) tributary water sharing among small farmer groups (iii) sub-catchment and (iv) catchment scale. The benefits of water sharing were evaluated based on the modelled reductions in the probability of an irrigation deficit occurring (reducing drought risks) and reduced licensed ‘headroom’ (spare capacity redeployed for more equitable allocation). The potential benefits of water sharing were found to increase with scale, but its impact was limited at high levels of drought severity due to regulatory drought management controls. The broader implications for water sharing to mitigate drought impacts, the barriers to wider uptake and the environmental consequences are discussed.
Highlights
Droughts occur in most regions of the world and have affected more people globally than any other natural hazard over the last 40 years [1]
The annual licensed volume and reported actual abstractions for 2018 for each farm business ranked by their total licensed volume (Figure 4) showed that most of the businesses had significant unused allocation. This unused licensed volume, The individual D-Risk drought risk profiles for each water-sharing group at a given spatial scale were converted to aggregated profiles to evaluate the potential benefits of water sharing, especially during drought years
By taking into account the current regulatory and drought management restrictions on irrigation abstraction, our analysis showed that water sharing does not completely remove drought risk due to the combination of water resources management constraints that are embedded in the volumetric licence limits to ensure sustainable abstraction and drought management protections such as abstraction restrictions at low river flows
Summary
Droughts occur in most regions of the world and have affected more people globally than any other natural hazard over the last 40 years [1]. In order to limit environmental impacts, such as the depletion of aquifers, low flows in rivers and degradation of aquatic habitats [10,11] associated with uncontrolled and inefficient abstraction, many countries have abstraction regimes with licences or permitting systems [12,13,14,15,16,17,18,19,20] These usually specify a fixed annual allocation of water but tend to be awarded on a ‘first come—first served’ basis leading to a sub-optimal and over-allocation of water. This is increasingly leading to pressure for more efficient water allocation that moves agricultural irrigation allocations to uses with higher economic value, in particular cities [5,21]
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