Water planning decisions are only as good as our ability to explain historical trends and make reasonable predictions of future water availability. But predicting water availability can be a challenge in rapidly growing regions, where human modifications of land and waterscapes are changing the hydrologic system. Yet, many regions of the world lack the long-term hydrologic monitoring records needed to understand past changes and predict future trends.We investigated this "predictions under change" problem in the data-scarce Thippagondanahalli (TG Halli) catchment of the Arkavathy sub-basin in southern India. Inflows into TG Halli reservoir have declined sharply since the 1970s. The causes of the drying are poorly understood, resulting in misdirected or counter-productive management responses.Five plausible hypotheses that could explain the decline were tested using data from field surveys and secondary sources: (1) changes in rainfall amount, seasonality and intensity; (2) increases in temperature; (3) groundwater extraction; (4) expansion of eucalyptus plantations; and (5) fragmentation of the river channel. Our results suggest that groundwater pumping, expansion of eucalyptus plantations and, to a lesser extent, channel fragmentation are much more likely to have caused the decline in surface flows in the TG Halli catchment than changing climate.The multiple-hypothesis approach presents a systematic way to quantify the relative contributions of proximate anthropogenic and climate drivers to hydrological change. The approach not only makes a meaningful contribution to the policy debate but also helps prioritize and design future research. The approach is a first step to conducting use-inspired socio-hydrologic research in a watershed. Challenges in rapidly growing, data-scarce regionsMaking hydrological predictions is a non-trivial problem in any context, but it is confounded by three issues encountered in rapidly changing, data-scarce regions: (i) non-stationarity arising from anthropogenic drivers, (ii) the sparse availability of historical data, and (iii) lack of original, place-based scientific research leading to oversimplified assumptions. ThePublished by Copernicus Publications on behalf of the European Geosciences Union.

Abstract. Water planning decisions are only as good as our ability to explain historical trends and make reasonable predictions of future water availability. But predicting water availability can be a challenge in rapidly growing regions, where human modifications of land and waterscapes are changing the hydrologic system. Yet, many regions of the world lack the long-term hydrologic monitoring records needed to understand past changes and predict future trends.We investigated this "predictions under change" problem in the data-scarce Thippagondanahalli (TG Halli) catchment of the Arkavathy sub-basin in southern India. Inflows into TG Halli reservoir have declined sharply since the 1970s. The causes of the drying are poorly understood, resulting in misdirected or counter-productive management responses.Five plausible hypotheses that could explain the decline were tested using data from field surveys and secondary sources: (1) changes in rainfall amount, seasonality and intensity; (2) increases in temperature; (3) groundwater extraction; (4) expansion of eucalyptus plantations; and (5) fragmentation of the river channel. Our results suggest that groundwater pumping, expansion of eucalyptus plantations and, to a lesser extent, channel fragmentation are much more likely to have caused the decline in surface flows in the TG Halli catchment than changing climate.The multiple-hypothesis approach presents a systematic way to quantify the relative contributions of proximate anthropogenic and climate drivers to hydrological change. The approach not only makes a meaningful contribution to the policy debate but also helps prioritize and design future research. The approach is a first step to conducting use-inspired socio-hydrologic research in a watershed.

This paper seeks to contribute to the limited literature on water governance in small towns in India. For assessing water governance, we propose a broad framework encompassing adequacy and affordability, equity, sustainability and responsiveness. Analytically, the concept of ‘service modality’ is expanded to include not only institutional arrangements but also water resource deployment, and placed within a framework that includes multiple contextual variables as well. We use this framework to carry out an inductive analysis by comparing water service delivery and governance in four small towns across two states (Karnataka and Tamil Nadu) in southern India. Apart from differences in size, the towns differ in the institutional arrangements – from fully municipal management to a combination to complete para-statal management – and in the deployment of water resources – only ground water to a mixed supply of ground and surface water (dual sourcing). Data were gathered using a combination of household surveys, metering, records, and interviews. Dual sourcing resulted in adequate supply and optimization vis-à-vis end uses. Inter-household inequity is driven by socio-economic differences amongst households, but can be mitigated to an extent by increasing public tap density. But water resource use is not physically or financially sustainable. The responsiveness to citizen needs was significantly higher when the distribution was done by the local governments. Separation of roles, with para-statals providing bulk supply of surface water, and local governments managing the distribution of this and groundwater, may be an optimal service modality.

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