CTARA

In the semi-arid lands of southern Kenya, a dynamic process of farmer-led irrigation has developed over the past two decades. It is characterised by short-term agreements to access land and water. Resident and migrant farmers, capital providers and local landowners have engaged in diverse partnerships to benefit from water and land along the Olkeriai sand river. This study aims to unravel which actors and motives drive the resulting highly dynamic forms of irrigation. Surveys, in-depth interviews and mapping exercises with farmers, capital providers and landowners were conducted over a period of 1.5 years. The results show that involved actors favour short-term lease and partnership arrangements and farmers frequently change fields along the river or leave the area and return. It is primarily the migrant farmers and capital providers who take decisions on when and where to move. They are informed by their experience with production factors, financial gains and losses, partner relati...

Farmers in dryland regions are highly vulnerable to rainfall variability. This vulnerability is unequal, as it is mediated by biophysical and social factors. Implementing policies for climate resilience requires identification of farmers who are most vulnerable to extreme events like dry spells. We develop a novel approach by conceptualizing dry spell vulnerability at the farm scale in terms of monsoon crop water deficit. Using inputs of weather, terrain, soil properties, land-use-land-cover, crop properties, and cadastral maps, our tool models an hourly soil water balance at 30 m × 30 m resolution and maps the crop water deficit under rainfed conditions. This is a good indicator of the relative sensitivity of farmers to dry spells and allows prioritization of interventions within the focus region. Our tool, developed and deployed within the Maharashtra State Project on Climate-Resilient Agriculture, is iteratively calibrated and refined. We present the result of one such iteration ...

Much work has been done on the computation of market equilibria. However due to strategic play by buyers, it is not clear whether these are actually observed in the market. Motivated by the observation that a buyer may derive a better payoff by feigning a different utility function and thereby manipulating the Fisher market equilibrium, we formulate the Fisher market game in which buyers strategize by posing different utility functions. We show that existence of a conflict-free allocation is a necessary condition for the Nash equilibria (NE) and also sufficient for the symmetric NE in this game. There are many NE with very different payoffs, and the Fisher equilibrium payoff is captured at a symmetric NE. We provide a complete polyhedral characterization of all the NE for the two-buyer market game. Surprisingly, all the NE of this game turn out to be symmetric and the corresponding payoffs constitute a piecewise linear concave curve. We also study the correlated equilibria of this game and show that third-party mediation does not help to achieve a better payoff than NE payoffs.

An asynchronous automaton consists of a set of processes that cooperate in processing letters of the input. Each letter read prompts some of the processes to synchronize and decide on a joint move according to a non-deterministic transition relation. Zielonka's theorem tells us that these automata can be determinized while retaining the synchronization structure. Unfortunately, this construction is indirect and yields a triple-exponential blow-up in size. We present a direct determinization procedure for asynchronous automata which generalizes the classical subset construction for finite-state automata. Our construction is only double-exponential and thus is the first to essentially match the lower bound.