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Groundwater overexploitation has been cited as one of the biggest threats to rural drinking water in India, but there is very little quantitative evidence. In this paper, we aim to understand (1) the extent of actual groundwater depletion and its impact on rural drinking water supply systems, (2) the primary driver of groundwater depletion and (3) the additional financial burden in finding new sources for water supply and increased O&M costs.We rely on temporal data from two Gram Panchayats (local administrative unit) near Bengaluru, in south India. Our study results confirm that groundwater depletion, in this hard rock aquifer region, is a severe problem, driven largely by agricultural water abstraction. Rural drinking water supply systems have had to catch up continuously with the falling water table, abandoning non-functional wells and drilling new borewells to replace them. This has resulted in a major financial burden to the Gram Panchayats both in terms of increased capital and O&M costs. Increased pumping costs associated with declining groundwater levels impose a major burden on these Gram Panchayats, which are severely in “electricity debt”. Hitherto, state and central government grants have paid for rural well installation in India, but these schemes are time bound, posing a threat to future drinking water security.

The Cauvery basin in southern India is experiencing transboundary issues due to increasing water demand. This study analysed water balance components and the impact of agricultural water management (AWM) interventions in the upper Cauvery catchment of the Cauvery basin. Results showed that the study catchment receives an average of 1280 mm of annual rainfall. Of this, 29% (370 mm) flows downstream, 54% (700 mm) contributes to evapotranspiration (ET) and 17% (215 mm) contributes to groundwater recharge and surface storage. Rainfall varies from 700 to 5400 mm and the Western Ghats (mountain pass) are the main source of freshwater generation. The estimated ET in different catchments ranged from 500 to 900 mm per annum. An increase in the allocation of fresh water supplied by all three reservoirs (Hemavathi, Harangi and KRS) was observed in the canal command areas, from 1450 million cubic metres (MCM) yr‾¹ in 1971–1980 to 3800 MCM yr‾¹ in 2001–2010. AWM interventions harvested 140–160 MCM (13–20 mm) of surface runoff upstream of the upper Cauvery and reduced inflow into the Krishnaraja Sagar reservoir by 2–6%. The study findings are useful for designing and planning suitable water management interventions at basin scale.

In this paper we explore the relation – discrepancies and correlations – between surface & groundwater practices in the Cauvery delta, to (re)connect science, policy makers and grassroots initiatives that aim for sustainable delta futures. Key is the fluid relationship between rain, run-off and water in the ground, which has been: 1) overshadowed by a prevalent surface water thinking long performed by state agencies, and 2) outflanked by a contemporary reality of overpumping groundwater. The role of knowledge (data) and tools such as models, provided by science and relied upon by policymakers, have in this context been incomplete and contested. With an inability to deal with contemporary challenges (by state agencies), communities are left to respond (and are looked at to fill the gaps). New developments in citizen science and remote sensing democratise data and offer new pathways. What is needed is a situated science – one that accounts for how science is done and how it informs policy and practice (and how it can be informed by practice). We use the development of our own surface-groundwater model – initially at odds with farmers perceptions and experiences – as a case in point

Worsening environmental conditions threaten to undermine progress in reducing rural poverty. Little is known, however, about the prospects for farmer adaptations to mitigate this threat, in particular through opportunities for income diversification presented by recent non-agricultural growth. We study the effects of increasing water scarcity in India using quasi-random, geologically determined differences in access to groundwater. The drying up of wells results in a precipitous and persistent decline in farm income and wealth, with little evidence of agricultural adaptation. However, labor reallocation to off-farm employment appears successful in maintaining overall income, particularly in locations with a more developed manufacturing sector. (JEL O13, O18, Q12, Q15, Q18, Q25, Q28)

There has been renewed interest in the performance, functionality, and sustainability of traditional small-scale storage interventions (check dams, farm bunds and tanks) used within semi-arid regions for the improvement of local water security and landscape preservation. The Central Groundwater Board of India is encouraging the construction of such interventions for the alleviation of water scarcity and to improve groundwater recharge. It is important for water resource management to understand the hydrological effect of these interventions at the basin scale. The quantification of small-scale interventions in hydrological modelling is often neglected, especially in large-scale modelling activities, as data availability is low and their hydrological functioning is uncertain. A version of the Global Water Availability Assessment (GWAVA) water resources model was developed to assess the impact of interventions on the water balance of the Cauvery Basin and two smaller sub-catchments. Model results demonstrate that farm bunds appear to have a negligible effect on the average annual simulated streamflow at the outlets of the two sub-catchments and the basin, whereas tanks and check dams have a more significant and time varying effect. The open water surface of the interventions contributed to an increase in evaporation losses across the catchment. The change in simulated groundwater storage with the inclusion of interventions was not as significant as catchment-scale literature and field studies suggest. The model adaption used in this study provides a step-change in the conceptualisation and quantification of the consequences of small-scale storage interventions in large- or basin-scale hydrological models.

Recently, there has been renewed interest in the performance and functionality of traditional small-scale storage interventions (check dams, farm bunds and tanks) used across India for the improvem...

Recently, there has been renewed interest in the utilisation of traditional small-scale storage interventions (check dams, field bunds and tanks) across India for the improvement of local water security. The Central Groundwater Board of India is encouraging the construction of interventions, such as check dams, field bunds and tanks, as the primary policy for the alleviation of water scarcity. It is of critical importance to understand the hydrological effect of these interventions at the small- and large-scale to maximise their impact and effectiveness. The quantification of small- scale interventions in hydrological modelling is often neglected, especially in large- scale modelling exercises. Although individually small, cumulatively these interventions may have a large effect on basin hydrology. A bespoke version of the Global Water AVailability Assessment (GWAVA) model was developed to incorporate the impact of interventions on the hydrology. Interventions were conceptualised within the model structure using local knowledge, observed data and adaptations of existing reservoir representations. The effect of interventions on the water balance of the Cauvery Basin (81 000 km2), Peninsula India, and various small sub-catchments (each approximately 3500 km2) was studied. To quantify the impact of small interventions, two model runs were generated. An initial simulation was performed including a representation of the check dams, field bunds and tanks thought to be within the catchments, and compared with a “reference” simulation where no interventions were included but instead were replaced by grassland. The percentage difference for each component of the water balance was determined as an indicator of the impact of the interventions. The inclusion of interventions increases the total annual evaporation across the basin and reduces the annual streamflow. Although the interventions are constructed to provide increased surface and groundwater storage within the agricultural and urban areas, the implementation resulted in a significant decrease in total annual water storage within the sub- catchments. The aquifer levels rise minimally in the eastern sub-catchments and exhibit no change in the western sub- catchments. The aquifer levels in the mid- basin remained unchanged with the implantation of interventions. Although the implementation of interventions are thought to increase the availability of groundwater at a local scale by upwards of two meters, the investigation using GWAVA suggest that aquifer levels are minimally affected. Based on the current understanding of interventions and the catchment hydrology, the wider effects of interventions on the water balance could be more detrimental to surface water security than anticipated and, thus, may not alleviate water poverty. The uncertainty related to the input data on interventions in the Cauvery may have affected the findings and thus further studies in regions with sufficient data availability and varying climate conditions may provide additional insight into the small- and large-scale effects of interventions.

Millions of people around the world are affected by water crises manifesting at different scales, such as increasing drought severity and flood risk, groundwater depletion, ecological degradation, poor sanitation, water pollution and its impact on human health. This global water crisis is increasingly interconnected and growing in complexity. Negative effects often result from a lack of understanding of wider economic and socio-cultural perspectives. More specifically, water crises can be deemed the intended or unintended consequences of long-term changes of social norms and values (or, more broadly, culture), ideology or political systems, which are not typically anticipated or accounted for in coping with water-related issues. Sociohydrology engages with these principles by examining the outcomes of water management and governance processes –successes and failures as well as the distribution of costs and benefits across social groups— themselves as subjects of scientific study. In this presentation, we show how feedback mechanisms between human and water systems can generate a wide range of phenomena (including crises) in different places around the world. Moreover, we argue that a generalized understanding of sociohydrological phenomena has an important role to play in informing policy processes while assisting communities, governments, civil society organizations and private actors to address the global water crisis and meet the Sustainable Development Goals, the societal grand challenge of our time.

Unregulated groundwater extraction has led to declining groundwater tables and increasing water scarcity in the Indian subcontinent. Understanding how farmers respond to this scarcity is important from multiple perspectives—equity in access, livelihood security and resource sustainability. We present a case from the rapidly urbanizing Arkavathy sub-basin near Bangalore city in southern India where irrigation is fully groundwater dependent. Using cross-sectional data from a stratified random sample of 333 farmers from 15 villages, we investigated the factors that determine their choice of crops under conditions of water scarcity and urbanization. Binary logit analysis showed that farmers with a large landholding respond by tapping deep groundwater using borewells. Multinomial logit analysis revealed that access to groundwater, variation in the proximity to the product market (city) and labour availability influence crop choice decisions. We observe that current responses indicate what has been characterized in the literature as chasing strategies. These largely favour well-off farmers and hence are inequitable. While the choice of water-intensive crops and unregulated pumping have aggravated water stress, the uptake of watersaving technologies among irrigated farmers has been low, showing that resource sustainability may not be a concern where non-farm diversification opportunities exist.

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.

Quantifying domestic water use at the household scale is crucial for any policy interventions towards ensuring adequate, equitable and safe water access. In developing country contexts, piped water supply is often one of several sources from which households access water and this is often unmetered. The most common approach to quantifying household water use from multiple sources is through household surveys. But there is no evidence that household surveys accurately estimate water use. This study utilized high-resolution pressure-sensor data as a reference to evaluate the effectiveness of conventional household survey methods through a sample of 82 households in Coimbatore city in South India. The pressure sensors produced detailed, continuous and accurate information on all sources of water accessed through the household storage infrastructure, but they were expensive and intrusive. Compared with pressure-sensor derived estimates of tap water use, household surveys alone fared very poorly. However, household surveys and well-designed water diaries of supply and pumping, coupled with simple one-time field measurements, emerged as a valid approach to quantifying household water use from taps under multiple source dependence.

Much of the research on climate change adaptation in rapidly urbanizing developing regions focuses primarily on adaptation or resilience as the goal, assumes that climate change is the major stress...

The complexity and heterogeneity of human water use over large spatial areas and decadal timescales can impede the understanding of hydrological change, particularly in regions with sparse monitoring of the water cycle. In the Arkavathy watershed in southern India, surface water inflows to major reservoirs decreased over a 40-year period during which urbanization, groundwater depletion, modification of the river network, and changes in agricultural practices also occurred. These multiple, interacting drivers combined with limited hydrological monitoring make attribution of the causes of diminishing water resources in the watershed challenging and impede effective policy responses. To mitigate these challenges, we developed a novel, spatially distributed dataset to understand hydrological change by characterizing the residual trends in surface water extent that remain after controlling for precipitation variations and comparing the trends with historical land use maps to assess human drivers of change. Using an automated classification approach with subpixel unmixing, we classified water extent in nearly 1700 man-made lakes, or tanks, in Landsat images from 1973 to 2010. The classification results compared well with a reference dataset of water extent of tanks (R2 = 0.95). We modeled the water extent of 42 clusters of tanks in a multiple regression on simple hydrological covariates (including precipitation) and time. Inter-annual variability in precipitation accounted for 63 % of the predicted variability in water extent. However, precipitation did not exhibit statistically significant trends in any part of the watershed. After controlling for precipitation variability, we found statistically significant temporal trends in water extent, both positive and negative, in 13 of the clusters. Based on a water balance argument, we inferred that these trends likely reflect a non-stationary relationship between precipitation and watershed runoff. Independently of precipitation, water extent increased in a region downstream of Bangalore, likely due to increased urban effluents, and declined in the northern portion of the Arkavathy. Comparison of the drying trends with land use indicated that they were most strongly associated with irrigated agriculture, sourced almost exclusively by groundwater. This suggests that groundwater abstraction was a major driver of hydrological change in this watershed. Disaggregating the watershed-scale hydrological response via remote sensing of surface water bodies over multiple decades yielded a spatially resolved characterization of hydrological change in an otherwise poorly monitored watershed. This approach presents an opportunity to understand hydrological change in heavily managed watersheds where surface water bodies integrate upstream runoff and can be delineated using satellite imagery.

Water security is a multi-faceted problem, going beyond mere balancing of supply and demand. Early attempts to quantify water security relied on static index based approaches that failed to acknowledge that human action is intrinsic to the water cycle. Human adaptation to environmental change and increasing spatial specialization in the modern world necessitate a more flexible and dynamic view of water security. Starting from first principles, and through application of simple water balance concepts to human-impacted water systems, we first develop a set of indicators for water insecurity. We then offer an approach to model these indicators as outcomes of coupled human-water systems to anticipate watershed trajectories under human impacts, predict water insecurity and inform appropriate action. In this way, far from being a static index, water security signifies a “safe operating subspace” within a three dimensional space that maps physical resource availability, infrastructure and economic choices.

India is one of the most water stressed countries in the world. However, despite appreciable increase in funding for water research, high quality science that is usable by stakeholders remains elusive. I argue that this can be attributed to the absence of research on questions that actually matter to stakeholders, unwillingness to transcend disciplinary boundaries, and the demise of fleld-work research culture in favour of computer simulation. Conventional wisdom is these trends are driven by what is publishable. However, there is an increasing interest in the international community in interdisciplinary, problem driven, empirical research. Using examples of my own research in Chennai and Bengaluru, on water scarcity in urbanising watersheds, I offer some methods and insights.

The arguments presented in Melsen et al. advance ideas in the “Panta Rhei” decade (2013–2022) of the International Association of Hydrological Sciences, which focuses on change in hydrology and soc...

Sociohydrology is the study of coupled human–water systems, building on the premise that water and human systems co-evolve: the state of the water system feeds back onto the human system, and vice versa, a situation denoted as "two-way coupling". A recent special issue in HESS/ESD, "Predictions under change: water, earth, and biota in the Anthropocene", includes a number of sociohydrologic publications that allow for a survey of the current state of understanding of sociohydrology and the dynamics and feedbacks that couple water and human systems together, of the research methodologies being employed to date, and of the normative and ethical issues raised by the study of sociohydrologic systems. Although sociohydrology is concerned with coupled human–water systems, the feedback may be filtered by a connection through natural or social systems, for example, the health of a fishery or through the global food trade, and therefore it may not always be possible to treat the human–water system in isolation. As part of a larger complex system, sociohydrology can draw on tools developed in the social–ecological and complex systems literature to further our sociohydrologic knowledge, and this is identified as a ripe area of future research.

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.

The developing world is rapidly urbanizing. One of the challenges associated with this growth will be to supply water to growing cities of the developing world. Traditional planning tools fare poorly over 30–50 year time horizons because these systems are changing so rapidly. Models that hold land use, economic patterns, governance systems or technology static over a long planning horizon could result in inaccurate predictions leading to sub-optimal or paradoxical outcomes. Most models fail to account for adaptive responses by humans that in turn influence water resource availability, resulting in coevolution of the human–water system. Is a particular trajectory inevitable given a city's natural resource endowment, is the trajectory purely driven by policy or are there tipping points in the evolution of a city's growth that shift it from one trajectory onto another? Socio-hydrology has been defined as a new science of water and people that will explicitly account for such bi-directional feedbacks. However, a particular challenge in incorporating such feedbacks is imagining technological, social and political futures that could fundamentally alter future water demand, allocation and use. This paper offers an alternative approach – the use of counterfactual trajectories – that allows policy insights to be gleaned without having to predict social futures. The approach allows us to "reimagine the past"; to observe how outcomes would differ if different decisions had been made. The paper presents a "socio-hydrological" model that simulates the feedbacks between the human, engineered and hydrological systems in Chennai, India over a 40-year period. The model offers several interesting insights. First, the study demonstrates that urban household water security goes beyond piped water supply. When piped supply fails, users turn to their own wells. If the wells dry up, consumers purchase expensive tanker water or curtail water use and thus become water insecure. Second, unsurprisingly, different initial conditions result in different trajectories. But initial advantages in piped infrastructure are eroded if the utility is unable to expand the piped system to keep up with growth. Both infrastructure and sound management decisions are necessary to ensure household water security although the impacts of mismanagement may not manifest until much later when the population has grown and a multi-year drought strikes. Third, natural resource endowments can limit the benefits of good policy and infrastructure. Cities can boost recharge through artificial recharge schemes. However, cities underlain by productive aquifers can better rely on groundwater as a buffer against drought, compared to cities with unproductive aquifers.

Addressing water security in the developing world involves predicting water availability under unprecedented rates of population and economic growth. Yet the combination of rapid change, inadequate data and human modifications to watersheds poses a challenge, as researchers face a poorly constrained water resources prediction problem. This case study of the data-scarce, upper Arkavathy watershed, near the city of Bengaluru in southern India, attempts to systematically explain the observed disappearance of surface and groundwater in recent decades. The study asks three questions: 1) Can we quantify the change attributable to different drivers? 2) Can we anticipate change? 3) What policy lessons can be drawn? Field experiments, isotopic studies, borewell scans and sensors were deployed to understand hydrologic processes over five years. These were used in a historical reconstruction of the catchment over three decades that replicates the decline. The multi-scale model of the upper Arkavathy, quantifies the contributions of soil and water conservation measures, groundwater depletion and eucalyptus plantations to the decline in surface and groundwater resources. The model results indicate that the catchment hydrology cannot be reconstructed without explicitly including human feedbacks. The system is influenced by both endogenous drivers (social feedbacks to changes in water availability such as irrigation efficiency improvements, soil and water conservation measures and deeper borewells) and exogenous drivers (technological change, pro-development governance and economic forces due to urbanization, which provided access to capital and markets for high-value crops). The research suggests that in a system where productivity of the landscape is limited by water, economic drivers will always push for maximization of water abstraction and use. Unsustainability of resource use is inevitable, in the absence of credible controls on abstraction and use.

This article addresses a gap in the water equity literature arising from the simultaneous use of surface water and groundwater in India. Using two diverse case studies – one agricultural (Kukdi) and one urban (Chennai) – we demonstrate how gaps in planning, design and policy exacerbate inequity. Groundwater abstraction from user wells allows wealthier users to both free-ride and capture a greater share of the resource. By converting a public resource to a private one, it worsens inequity and jeopardizes the sustainability of water projects. The article suggests that better monitoring, inter-agency coordination and rethinking water entitlements and norms are needed for going forward.

Developing countries are faced with the dual challenge of adapting to climate change even as current water needs remain unmet. We review the literature specifically on water provisioning in this context to see what insights can be derived for achieving better integration across disciplinary and research-practice divides. We identify several disconnects in the climate-vulnerability literature: scale mismatches, missing linkages, multiple stressors and concerns, concepts emerging from different intellectual traditions, and inattention to stakeholder priorities. Recent work attempts to overcome some of these challenges. At the conceptual level, the coupled human–environment systems (CHES) framework forces analysts to address scale mismatches and multiple stressors, although given its breadth, applications of CHES still tend to follow disciplinary divides. At the methodological level, participatory/mediated modelling forces attention to stakeholder priorities while historical/comparative methods provide an empirical assessment of long-term adaptation not just short-term reactive strategies. In conclusion, we suggest ways of further integrating the strengths of these approaches in the context of water provisioning in developing countries. Addresses

Economic valuation of ecosystem benefits and their aggregation in a benefit–cost analysis (BCA) framework is the norm in mainstream environmental economics. But valuation and BCA have also attracted criticisms. ‘Internal’ criticisms point to the absence of alternative scenarios in valuation, overlooking of ecological trade-offs and dis-services, and inattention to context. Others criticize aggregation across diverse stakeholders and the problem of non-monetizable benefits, and dismiss BCA as fatally flawed. They suggest approaches such as deliberative decision-making and multi-criteria analysis. We propose a middle path that uses the strengths of economic analysis for decision support while avoiding the pitfalls. We disaggregate economic impacts by stakeholder groups, link ecosystem changes to benefits as well as dis-benefits, and examine how socio-technological context shapes the magnitude of economic impact. We illustrate this approach by studying the impact of creating the Biligiri Rangaswamy Temple wildlife sanctuary in the Western Ghats forests of southern India. Our analysis shows that while some stakeholders are net beneficiaries, others are net losers. Changes in forest rights, irrigation technologies, and ecosystem dynamics influence the magnitude of benefits and sometimes convert gainers into losers. Such disaggregated analysis can provide useful information for deliberative decision-making and important academic insights on how economic value is generated.

While there is consensus that urbanization is one of the major trends of the 21 st century in developing countries, there is debate as to whether urbanization will increase or decrease vulnerability to droughts. Here we examine the relationship between urbanization and water vulnerability for a fast-growing city, Chennai, India, using a coupled human–environment systems (CHES) modeling approach. Although the link between urbanization and water vulnerability is highly site-specific, our results show some generalizable factors exist. First, the urban transformation of the water system is decentralized as irrigation wells are converted to domestic wells by private individuals, and not by the municipal authority. Second, urban vulnerability to water shortages depends on a combination of several factors: the formal water infrastructure, the rate and spatial pattern of land use change, adaptation by households and the characteristics of the ground and surface water system. Third, vulnerability is dynamic, spatially variable and scale dependent. Even as household investments in private wells make individual households less vulnerable, over time and cumulatively, they make the entire region more vulnerable. Taken together, the results suggest that in order to reduce vulnerability to water shortages, there is a need for new forms of urban governance and planning institutions that are capable of managing both centralized actions by utilities and decentralized actions by millions of households.

Many developing world cities have seen the emergence of informal markets where private tanker truck operators transport water extracted from peri-urban wells to urban consumers. This study adopted a systems-modelling approach to analyzing the informal tanker market in India. The results indicate that the demand for tanker supply was caused by lack of groundwater availability in private wells as well as unreliable piped supply. The study shows that two groundwater factors are relevant: depth to water and aquifer productivity. Together, these could explain the difference in spatial, temporal and consumer-specific variations in tanker dependence.

This article describes the field application of small, low-cost robots for remote surface data collection and an automated workflow to support water balance computations and hydrologic understanding where water availability data is sparse. Current elevation measurement approaches, such as manual surveying and LiDAR, are costly and infrequent, leading to potential inefficiencies for quantifying the dynamic hydrologic storage capacity of the land surface over large areas. Experiments to evaluate a team of two different robots, including an unmanned aerial vehicle (UAV) and an unmanned surface vehicle (USV), to collect hydrologic surface data utilizing sonar and visual sensors were conducted at three different field sites within the Arkavathy Basin river network located near Bangalore in Karnataka, South India. Visual sensors were used on the UAV to capture high resolution imagery for topographic characterization, and sonar sensors were deployed on the USV to capture bathymetric readings; the data streams were fused in an automated workflow to determine the storage capacity of agricultural reservoirs (also known as ``tanks'') at the three field sites. This study suggests: (i) this robot-assisted methodology is low-cost and suitable for novice users, and (ii) storage capacity data collected at previously unmapped locations revealed strong power-type relationships between surface area, stage, and storage volume, which can be incorporated into modeling of landscape-scale hydrology. This methodology is of importance to water researchers and practitioners because it produces local, high-resolution representations of bathymetry and topography and enables water balance computations at small-watershed scales, which offer insight into the present-day dynamics of a strongly human impacted watershed.

Growing pressure on the world’s water resources is having major impacts on our social and economic well-being. Even as the planet’s endowment of water is expected to remain constant, human appropriation of water, already at 50 percent by some measures, is expected to increase further (Postel et al. 1996). Pressures on water resources are likely to worsen in response to population growth, shifts toward more meat-based diets, climate change, and other challenges. Moreover, the world’s water is increasingly becoming degraded in quality, raising the cost of treatment and threatening human and ecosystem health (Palaniappan et al. 2010). Furthermore, the physical availability of freshwater resources does not guarantee that a safe, affordable water supply is available to all. At least 780 million people do not have access to clean drinking water, some 2.5 billion people lack access to safe sanitation systems, and 2–5 million people—mainly children—die as a result of preventable water-related diseases every year (Gleick 2002; UN 2009; WHO and UNICEF 2012).

Globally, many different kinds of water resources management issues call for policy- and infrastructure-based responses. Yet responsible decision-making about water resources management raises a fundamental challenge for hydrologists: making predictions about water resources on decadal- to century-long timescales. Obtaining insight into hydrologic futures over 100 yr timescales forces researchers to address internal and exogenous changes in the properties of hydrologic systems. To do this, new hydrologic research must identify, describe and model feedbacks between water and other changing, coupled environmental subsystems. These models must be constrained to yield useful insights, despite the many likely sources of uncertainty in their predictions. Chief among these uncertainties are the impacts of the increasing role of human intervention in the global water cycle – a defining challenge for hydrology in the Anthropocene. Here we present a research agenda that proposes a suite of strategies to address these challenges from the perspectives of hydrologic science research. The research agenda focuses on the development of co-evolutionary hydrologic modeling to explore coupling across systems, and to address the implications of this coupling on the long-time behavior of the coupled systems. Three research directions support the development of these models: hydrologic reconstruction, comparative hydrology and model-data learning. These strategies focus on understanding hydrologic processes and feedbacks over long timescales, across many locations, and through strategic coupling of observational and model data in specific systems. We highlight the value of use-inspired and team-based science that is motivated by real-world hydrologic problems but targets improvements in fundamental understanding to support decision-making and management. Fully realizing the potential of this approach will ultimately require detailed integration of social science and physical science understanding of water systems, and is a priority for the developing field of sociohydrology.

The new Scientific Decade 2013-2022 of IAHS, entitled "Panta Rhei-Everything Flows", is dedicated to research activities on change in hydrology and society. The purpose of Panta Rhei is to reach an improved interpretation of the processes governing the water cycle by focusing on their changing dynamics in connection with rapidly changing human systems. The practical aim is to improve our capability to make predictions of water resources dynamics to support sustainable societal development in a changing environment. The concept implies a focus on hydrological systems as a changing interface between environment and society, whose dynamics are essential to determine water security, human safety and development, and to set priorities for environmental management. The Scientific Decade 2013-2022 will devise innovative theoretical blueprints for the representation of processes including change and will focus on advanced monitoring and data analysis techniques. Interdisciplinarity will be sought by increased efforts to connect with the socio-economic sciences and geosciences in general. This paper presents a summary of the Science Plan of Panta Rhei, its targets, research questions and expected outcomes.; La décennie scientifique 2013–2022 de l’AISH est intitulée “Panta Rhei-Tout s’écoule” et est dédiée à des activités de recherche concernant la question du changement hydrologique et sociétal. La vocation de “Panta Rhei” est d’atteindre une meilleure compréhension des processus régissant le cycle de l’eau en se concentrant sur leur dynamique de changement, en lien avec les systèmes anthropiques qui changent eux–mêmes rapidement. L’objectif opérationnel est d’améliorer notre capacité à prévoir la dynamique des ressources en eau au service d’un développement sociétal durable dans un environnement changeant. Le concept implique une focalisation sur les systèmes hydrologiques vus comme une interface changeante entre environnement et société, dont les dynamiques sont essentielles à la sécurité hydrique, au développement humain, et au choix de priorités dans la gestion de l’environnement. La décennie scientifique 2013–2022 vise la conception de schémas théoriques innovants pour représenter les processus et leur évolution, et insistera sur les techniques avancées d’observation et d’analyse de données. On recherchera l’interdisciplinarité avec les sciences socio-économiques et les géosciences en général. Cet article présente une synthèse du programme scientifique “Panta Rhei”, ses objectifs, ses questions de recherche et les résultats que l’on en attend.

Freshwater scarcity has been cited as the major crisis of the 21st century, but it is surprisingly hard to describe the nature of the global water crisis. We conducted a meta- analysis of 22 coupled human– water system case studies, using qualitative comparison analysis (QCA) to identify water resource system outcomes and the factors that drive them. The cases exhibited different outcomes for human wellbeing that could be grouped into a six “syndromes ”: groundwater depletion, ecological destruction, drought-driven conflicts, unmet subsistence needs, resource capture by elite, and water reallocation to nature. For syndromes that were not successful adaptations, three characteristics gave cause for concern: (1) unsustainability —a decline in the water stock or ecosystem function that could result in a long-term steep decline in future human wellbeing; (2) vulnerability —high variability in water resource availability combined with inadequate coping capacity, leading to temporary drops in human wellbeing; (3) chronic scarcity —persistent inadequate access and hence low conditions of human wellbeing. All syndromes could be explained by a limited set of causal factors that fell into four categories: demand changes, supply changes, governance systems, and infrastructure/technology. By considering basins as members of syndrome classes and tracing common causal pathways of water crises, water resource analysts and planners might develop improved water policies aimed at reducing vulnerability, inequity, and unsustainability of freshwater systems.

[1] Indian megacities face severe water supply problems owing to factors ranging from growing population to high municipal pipe leakage rates; no Indian city provides 24/7 water supply. Current approaches to addressing the problem have been “utility centric,” overlooking the significance of decentralized activities by consumers, groundwater extraction via private wells, and aquifer recharge by rainwater harvesting. We propose a framework that makes it possible to evaluate a wider range of centralized and decentralized policies than previously considered. The framework was used to simulate water supply and demand in a simulation model of Chennai, India. Three very different policies, supply augmentation, efficiency improvement, and rainwater harvesting, were evaluated using the model. The model results showed that none of the three policies perfectly satisfied our criteria of efficiency, reliability, equity, financial viability, and revenue generation. Instead, a combination of rainwater harvesting and efficiency improvement best meets these criteria.

[1] In this paper, we discuss a challenging water resources problem in a developing world city, Chennai, India. The goal is to reconstruct past system behavior and diagnose the causes of a major water crisis. In order to do this, we develop a hydrologic-engineering-economic model to address the complexity of urban water supply arising from consumers' dependence on multiple interconnected sources of water. We integrate different components of the urban water system: water flowing into the reservoir system; diversion and distribution by the public water utility; groundwater flow in the aquifer beneath the city; supply, demand, and prices in the informal tanker-truck-based water market; and consumer behavior. Both the economic and physical impacts of consumers' dependence on multiple sources of water are quantified. The model is calibrated over the period 2002–2006 using a range of hydrologic and socio-economic data. The model's results highlight the inadequacy of the reservoir system and the buffering role played by the urban aquifer and consumers' coping investments during multiyear droughts.