The relation between rainfall and water accumulated in reservoirs comprises nonlinear feedbacks. Here we show that they may generate alternative equilibrium regimes, one of high water-volume, the other of low water-volume. Reservoirs can be seen as socio-environmental systems at risk of regime shifts, characteristic of tipping point transitions. We analyze data from stored water, rainfall, and water inflow and outflow in the main reservoir serving the metropolitan area of São Paulo, Brazil, by means of indicators of critical regime shifts, and find a strong signal of a transition.

Droughts will likely become more frequent, greater in magnitude and longer in duration in the future due to climate change. Already in the present climate, a variety of drought events may occur with different exceedance frequencies. These frequencies are becoming more uncertain due to climate change. Many methods in support of drought risk management focus on providing insight into changing drought frequencies, and use water supply reliability as a key decision criterion.

The law and policy frameworks for allocation or reallocation of water to different uses, or within a category of use, remain underdeveloped in India. This paper intends providing a starting point for a conversation on the law and policy dimensions of inter-sectoral water allocation. Focusing on a specific inter-sectoral water allocation conflict in Rajsamand District, Rajasthan, it illustrates gaps in the existing law and policy frameworks and highlights multiple issues that need to be addressed.