Diseño del Experimento para la comparación de las técnicas

In conjunction with the model developments described above, there is potential to apply the integrated hydro-economic modelling framework to evaluate a wide range of aspects of the man- agement of coupled agricultural groundwater systems. Examples of a number of ongoing/planned model applications are discussed briefly below.

Analysis of groundwater management policies

In this thesis, a simplified set of policy analyses have been conducted to evaluate the long- term impacts of groundwater abstraction quotas on both agricultural production and aquifer sustainability. However, as discussed in Section 4.3.4, water use quotas are only one potential mechanism through which groundwater can be regulated. Future work will seek to apply the modelling framework developed in this thesis to compare the hydrological and agro-economic

impacts of water use quotas with a wider range of alternative policies, such as energy quotas and pricing of water or energy. This comparative analysis will evaluate how the effectiveness and acceptability of each policy is influenced by a number of important factors that were not considered explicitly in this thesis. In particular, future work will focus on evaluating how the impacts of policies designed to maintain well yield differ at the micro-level due heterogeneity in farmer behaviour and production conditions (Madani and Dinar, 2013; Mulligan et al., 2014), and how the value of regulations are affected by social costs associated with monitoring and enforcement (Koundouri, 2004; Blanco-Gutiérrez et al., 2011).

The future analyses proposed above focuses on comparing the impacts of independently implemented policies. However, in practice, a broader range of regulations may be applied si- multaneously that may be overlapping and non-complementary. It would be valuable therefore to evaluate the potential gains and losses that might occur from different portfolios of regulatory management options. For example, previous research has suggested that energy conservation policies, such as interruptible energy supply contracts to reduce peak loading, may inadvertently lead farmers’ to increase groundwater pumping to reduce risks associated with future water inse- curity (Scott, 2013; Mieno, 2014). However, existing work has not considered how the response of farmers groundwater use to interruptible energy supply is affected by available well pumping capacity or the simultaneous presence of regulations that may aim to limit groundwater pumping. Ongoing research therefore is seeking to apply a refined version of the integrated model developed in this thesis to help to develop improved understanding about how farmer decision making may be affected by interactions between energy and water use policies, and what implications this may have for long-term aquifer sustainability.

Potential of groundwater-fed irrigation in low-yielding aquifers

Well yield may be constrained by reductions in saturated thickness, as has been considered in this thesis, but may also be restricted by the natural geology of an aquifer. Wells that yield

flow rates of less than 5 L s-1 are common in crystalline basement fractured rock aquifers that

underlie large areas of regions such as Sub-Saharan Africa (MacDonald et al., 2012). However, expansion of groundwater-fed irrigation often is still cited as a potential solution to problems of food insecurity and poverty in these regions without consideration of the constraints that may be imposed by low well productivity (Cassman and Grassini, 2013; Pavelic et al., 2013; Xie et al., 2014). In future work, it is planned to apply the integrated modelling framework to develop more realistic estimates of the potential capacity of groundwater-fed irrigation across a range of settings in Sub-Saharan Africa. Research will consider the effects of geology on well yields, along

with other important determinants of long-term well performance such as borehole construction, pump type, and irrigation technology. It is hoped that the results will provide new knowledge about how groundwater resources can be developed sustainably and reliably in order to enable farmers’ to adapt successfully to the risks posed by climate variability and change.

Integration with existing management tools

A valuable area for further work would also be to explore how the key findings and approaches presented in this thesis could be incorporated directly in to existing real-world groundwater man- agement tools. In the Republican River Basin, for example, a MODFLOW groundwater model is the primary tool that is used by the regulator to quantify the impacts of irrigation pumping on groundwater levels and streamflow, and to define allocations of water between users (Vincent, 2003). However, the findings presented in this thesis suggest that the ability of this model to reliably inform management may be limited as it does not consider how simulated changes in groundwater levels will affect well yields or how hydrological change is driven by heterogeneity in individual farmer behaviour across the basin. Future work therefore could seek to adapt the current model to enable predictions of groundwater depth to be translated in to estimates of well yields, for example by incorporating multiple SPIDERR models in to the regional MODFLOW model (Upton et al., 2013) or by developing statistical relationships between saturated thickness and well yield (Hecox et al., 2002). In turn, the model of farmer decision making proposed in this thesis could be calibrated to long-term records of individual groundwater pumping in the basin and linked to the adapted MODFLOW model. These adaptations would enhance the ability of the current management model to capture key feedbacks between groundwater and producer behaviour, and would hopefully contribute to improving the regulators ability to predict reliably the effectiveness of alternative policy options in the basin.