Each of the cells provides selected examples of public instruments that could affect groundwater management in agriculture. It, however, excludes private approaches supported by legal instruments, such as adjudication or litigation, that do not fit into any of the above-discussed categories. As noted in Chapter 2, just as groundwater systems are diverse and associated with specific challenges, not all options will be useful in all contexts. The next section proposes elements of a model to help identify factors of differentiation for choice.