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Rangecroft et al. provide an important and interesting paper on the challenges of interdisciplinary research and fieldwork with participants in water resource management. The paper shows the challenges of interaction between their research areas and demonstrates the importance of how a researcher interacts with their selected study sites. My key points reflect the use of different methodologies within social and natural sciences and across them as well as the main challenge of who has the power to influence the research directions. Research is not value-free and is highly influenced by one's own training and knowledge, which needs to be addressed in the research activities. Finally, an option might be to move beyond interdisciplinary constraints and to work within a stronger transdisciplinary framework. Water research very much needs to interact with non-academic people to understand the challenges and possible solutions. [ABSTRACT FROM AUTHOR]

Rangecroft et al. (2021) offer a set of principles for conducting interdisciplinary research and fieldwork with participants from a hydrologist perspective. In this invited paper, I present some thoughts from a social scientist's perspective, not to disagree with their points but to add to them. Specifically, I use my sociology background and interdisciplinary experiences to reflect on qualitative evaluative criteria, power dynamics in the scientific community, barriers to interdisciplinary research, and approaches to overcome obstacles. Individual researchers can educate themselves about other disciplines, and there are also opportunities for institutional change on the part of universities, funders, and journals to support interdisciplinary work. I am enthusiastic about the emerging hydrology–social science collaborations I am witnessing. Indeed, I hope that more of my social science colleagues will see the unlimited potential of studying water systems with hydrologists and engineers, as I have. [ABSTRACT FROM AUTHOR]

Monitoring and predicting river floods have always been of concern for hydrologists. Anomalies in flow patterns alert us of upcoming events. The effect of such anomalies on the multifractality and nonlinear dynamics of the river flow is investigated in this research. The river flow of the River Trent in England from 2018 to 2019 was dissected using the multifractal, power spectrum, and phase space reconstruction techniques. Results show a reduction in multifractality strength before the anomalies in the time series. Moreover, receding trajectories from the attractor in the phase space and augmentation of the power spectrum confirmed a decline in flow multifractality due to anomalies. A compliance comparison of multifractality reduction before anomalies in river flow leads to predicting river floods approximately 12 days in advance. Furthermore, if the multifractal strength does not return to its equilibrium, this is a warning that floods are expected in the near future (less than 10 days). [ABSTRACT FROM AUTHOR]

To understand two-way linkages between water and society, achieve sustainable water management, and effectively communicate science and policy outcomes, Rangecroft et al. (2021) highlight the need for interdisciplinary collaboration between hydrologists and social scientists and outline considerations for conducting fieldwork with participants.1 In this discussion, I expand upon Rangecroft et al. (2021) to propose two contributions of qualitative social science for research about social-hydrological systems. First, qualitative social science research can help build an understanding of the lived experiences and perspectives of individuals within hydrological systems with the aim of sustainable water management. Second, drawing from a constructivist theoretical framework, qualitative social science research can highlight nuance and complexity within social-hydrological systems. In my discussion of these contributions, I provide real-world examples of effective data integration from research on the impacts of natural hazards, groundwater governance, understanding systematic vulnerabilities and adaptation to water scarcity, and sustainability science and planning. [ABSTRACT FROM AUTHOR]

In this reply to Thaler, we take the opportunity to explore two main aspects of his piece to continue the discussion: (1) the integration of data from the social and natural sciences, and (2) the importance of transdisciplinary research. We agree, and highlight that necessary learning, reflections and participation processes are time-intensive for researchers, practitioners and participants. We believe that these discussion pieces are important for informing, engaging, and debating challenges and practices, providing continued opportunities to learn from one another, enabling new forms of research and collaborations to flourish. [ABSTRACT FROM AUTHOR]

Socio-hydrology has recently garnered attention as a promising research paradigm among hydrologists. In this paper, we argue that viewing the socio-hydrological systems as a network of causal factors can assist in these efforts by revealing emergent properties of socio-hydrological systems. These factors, which are neither actors nor affiliations but symbolic representations of miscellaneous phenomena, represent the key variables affecting socio-hydrological system behaviour. Despite being crucial for understanding system dynamics, these factors are not captured by most equations of coupled human–water coevolutionary models. To demonstrate our method, we use qualitative case study research to analyse the Jaguaribe Basin in Ceará State-Brazil as a network of factors, i.e. mental conceptions, and representations of water resource management experts. We show that most results are unsurprising, exhibiting expected causal relationships. However, there was at least one unexpected result, which showed that the variable "conflict" was the single most sensitive variable to systemic evolution. [ABSTRACT FROM AUTHOR]

In this reply we thank both authors for their thoughtful insights on our original opinion piece "Guiding principles for hydrologists conducting interdisciplinary research and fieldwork with participants." We believe these discussions will help to inspire and guide current and future researchers and illustrate how to continue to bring together physical and social data, experiences, and perspectives, and bridge the gap between the two disciplines with respect to socio-hydrological topics. Furthermore, we are confident that these insights and experiences will help foster a deeper understanding for hydrologists and natural scientists engaging with these discussions and research. Here we focus on two important themes that cut across both Quandt and Haeffner's replies: (1) further discussions on the importance of perceptions and lived experiences; and (2) further discussions on collaborative working and some of the major external barriers. [ABSTRACT FROM AUTHOR]

To explore and address complex water-related issues, true collaborative, interdisciplinary research at the interface of hydrology and social science is necessary. Accordingly, hydrologists are increasingly working with social sciences and becoming involved in fieldwork with participants. With the overarching aim of facilitating collaboration and interdisciplinary water research, here we discuss important considerations and guiding principles for hydrologists, both those new to and those already familiar with interdisciplinary research, who are: (i) involved in fieldwork with participants; and (ii) working more collaboratively with social scientists. Drawing on first-hand experiences, this paper combines theory and experience from hydrologists and social scientists from their various interdisciplinary research projects to better understand key ethical, theoretical and practical considerations when working with participants. Complementary to this, we discuss the barriers and opportunities in collaborative interdisciplinary research. Facilitating these practices and understandings for hydrologists is essential to strengthen collaboration and to develop more holistic, successful research. [ABSTRACT FROM AUTHOR]

There is an increasing need for accurate groundwater-level (GWL) prediction to support effective seasonal water management. It is desirable for forecasting tools to be not only accurate but also accessible for decision-makers. We test the Prophet forecasting procedure, an open-source code released by Facebook, to address these challenges. It is based on an additive model considering non-periodic changes and periodic components in a Bayesian framework with easily-interpretable parameters. Predictions of daily GWL data in an area affected by pumping near a tourist complex in the Ramsar wetland area of Doñana (Spain) are compared to other forecasting methods. Prophet outperforms most methods in predicting GWL making it a fast and flexible forecasting tool for hydrologists and water managers. Furthermore, it allows gaining insight into the influence of each component of the forecast separately, helping to assess the hydrodynamic response to external drivers such as groundwater pumping. [ABSTRACT FROM AUTHOR]

R is an open-source statistical language that is supported by a large user community with many benefits for use in watershed analysis. R has been used widely in the Canadian research community and Canadian researchers have contributed numerous R packages with specific applications (e.g. seas, GEVcdn, RHtests, tidyhydat, FlowScreen). Here a new R package, CSHShydRology, is introduced that combines functions developed by hydrologists across Canada. [ABSTRACT FROM AUTHOR]

This paper highlights mistakes that have helped shape my professional career. I use examples of personal, as well as technical failures to explore some guiding principles that I have found useful when navigating my professional journey. It is only the rarest of technical gurus who can afford to ignore the limitations of their personal interactions: to be impactful, the rest of us need to give as much, if not more, attention to soft skills than we do to our technical ones. I thus discuss the qualities that I think are needed to leverage technical strengths, and I outline some professional behaviours that I think are required to be effective. I also outline some high level technical themes that I have found important as a hydrologist. These cover the challenges of extrapolation, the analysis of joint interactions in compound events, the differentiation between hydrologic change and variability, and the value of separately considering different sources of uncertainty. [ABSTRACT FROM AUTHOR]

The sharing of data and collection of new data are both essential, but they are not inherently complementary. When data are openly available, researchers may be motivated to use those data rather than collect more because field work has costs and risks. The competitive advantage to those who do not put resources towards fieldwork may discourage field hydrology. Allocating efforts towards generating field data, which benefits hydrological sciences, is not necessarily best for individual hydrologists, especially in an era of open data. The objective of this work is to open a conversation on whether individuals’ best interests may contrast with the community’s desire for new observations. If the community wants new field observations, there is a need to consider the shifting balance of incentives and disincentives for pursuing field studies in hydrology. [ABSTRACT FROM AUTHOR]

The complexities of the Prairie watersheds, including potholes, drainage interconnectivities, changing land-use patterns, dynamic watershed boundaries and hydro-meteorological factors, have made hydrological modelling on Prairie watersheds one of the most complex task for hydrologists and operational hydrological forecasters. In this study, four hydrological models (WATFLOOD, HBV-EC, HSPF and HEC-HMS) were developed, calibrated and tested for their efficiency and accuracy to be used as operational flood forecasting tools. The Upper Assiniboine River, which flows into the Shellmouth Reservoir, Canada, was selected for the analysis. The performance of the models was evaluated by the standard statistical methods: the Nash-Sutcliffe efficiency coefficient, correlation coefficient, root mean squared error, mean absolute relative error and deviation of runoff volumes. The models were evaluated on their accuracy in simulating the observed runoff for calibration and verification periods (2005-2015 and 1994-2004, respectively) and also their use in operational forecasting of the 2016 and 2017 runoff. [ABSTRACT FROM AUTHOR]

To promote the advancement of novel observation techniques that may lead to new sources of information to help better understand the hydrological cycle, the International Association of Hydrological Sciences (IAHS) established the Measurements and Observations in the XXI century (MOXXI) Working Group in July 2013. The group comprises a growing community of tech-enthusiastic hydrologists that design and develop their own sensing systems, adopt a multi-disciplinary perspective in tackling complex observations, often use low-cost equipment intended for other applications to build innovative sensors, or perform opportunistic measurements. This paper states the objectives of the group and reviews major advances carried out by MOXXI members toward the advancement of hydrological sciences. Challenges and opportunities are outlined to provide strategic guidance for advancement of measurement, and thus discovery. [ABSTRACT FROM AUTHOR]

Floods are occurring more frequently nowadays. The most common parameter used to analyse the flood severity is average recurrence interval (ARI). Very often, hydrologist found that the severity of flood is 100-year ARI. However, there is a possibility that the 100-year ARI flood severity will hit the same place again after a few months later. The two main possible reasons are (1) future warmer temperatures will increase future extreme precipitation extremes and (2) limited length recorded rainfall data had derived inaccurate Intensity duration frequency (IDF) curves. Therefore, there is an initiative in this study to derive future IDF curve by considering the future rainfall using ‘delta’ approach. The annual maximum precipitations for 2020s, 2050s and 2080s are generated using Statistical Downscaling Model (SDSM), neural network (NN) with scale conjugate gradient and Cuckoo search optimization algorithms. The selected study rainfall station is Kuching Airport. Results revealed that the newly projected IDF curves at various durations and ARIs are slightly higher than historical IDF curve. However, this research is still in the nascent stage and the results obtained are not finalized yet. More investigation works are carried out currently to establish reliable relationships between daily and sub-daily extreme precipitations based on the scaling general extreme value distribution. [ABSTRACT FROM PUBLISHER]

Dealing with uncertainty is key in socio-hydrological analysis. As such, thinking through what uncertainties mean for whom and when is key. This discussion contribution introduces three issues related to defining uncertainties. The first issue deals with the problem of defining uncertainty as a given external reality. The second issue deals with who decides about relevant uncertainties. The third issue deals with the issue whether coupled human-hydrological systems can be seen as existing on their own. Finally, the text provides two examples of hydrological research that try to be explicit about our dealing with multiple (interpretations of) realities. [ABSTRACT FROM AUTHOR]

Dealing with uncertainty is key in socio-hydrological analysis. As such, thinking through what uncertainties mean for whom and when is key. This discussion contribution introduces three issues related to defining uncertainties. The first issue deals with the problem of defining uncertainty as a given external reality. The second issue deals with who decides about relevant uncertainties. The third issue deals with the issue whether coupled human-hydrological systems can be seen as existing on their own. Finally, the text provides two examples of hydrological research that try to be explicit about our dealing with multiple (interpretations of) realities. [ABSTRACT FROM AUTHOR]

The Rational Formula is the most applied equation in practical hydrology due to its simplicity and the effective compromise between theory and data availability. Although the Rational Formula has several drawbacks, it is reliable and surprisingly accurate considering the paucity of input information. However, after more than a century, the recent progress in computational ability, theory and large-scale monitoring compel us to try to suggest a more advanced yet still empirical procedure for estimating peak discharge in small and ungauged basins. In this paper, an alternative empirical procedure is described and discussed, and then a discussion as to whether the Rational Formula is still necessary is presented. The presented methodology integrates the three standard steps of the common event-based approach (design hyetograph, rainfall excess and rainfall–runoff transformation) accurately adapted for application with a lack of observed data. The proposed procedure requires the same input information as necessary for application of the Rational Formula (soil properties, intensity–duration–frequency rainfall curves andTc) and provides both the peak discharge and the design hydrograph shape and, most importantly, reduces the subjectivity of the hydrologist in its application.Editor D. Koutsoyiannis [ABSTRACT FROM AUTHOR]

In this paper we investigate the impact of model mis-specification, in terms of the dependence structure in the extremes of a spatial process, on the estimation of key quantities that are of interest to hydrologists and engineers. For example, it is often the case that severe flooding occurs as a result of the observation of rainfall extremes at several locations in a region simultaneously. Thus, practitioners might be interested in estimates of the joint exceedance probability of some high levels across these locations. It is likely that there will be spatial dependence present between the extremes, and this should be properly accounted for when estimating such probabilities. We compare the use of standard models from the geostatistics literature with max-stables models from extreme value theory. We find that, in some situations, using an incorrect spatial model for our extremes results in a significant under-estimation of these probabilities which – in flood defence terms – could lead to substantial under-protection. [ABSTRACT FROM AUTHOR]

This review paper critically examines one of the most popular flood hydrograph modelling techniques for ungauged basins, the synthetic unit hydrograph (SUH), and its recent developments and advances. For this purpose, the SUH models were first grouped into four main classes, as follows: (a) traditional or empirical models; (b) conceptual models; (c) probabilistic models; and (d) geomorphological models. It was found that the geomorphological class is the most useful and interesting, since it is able to employ topographic information, so limiting the role of the calibration parameters. This review is expected to be helpful to hydrologists, water managers and decision-makers searching for models to study the flood hydrograph, modelling techniques and related processes in ungauged basins. It was completed as the International Association of Hydrological Sciences (IAHS) Decade (2003–2012) on predictions in ungauged basins (PUB), drew to a close. EditorD. Koutsoyiannis;Associate editorS. Grimaldi CitationSingh, P.K., Mishra, S.K., and Jain, M.K., 2013. A review of the Synthetic Unit Hydrograph: from the empirical UH to advanced geomorphological methods.Hydrological Sciences Journal, 59 (2), 239–261. [ABSTRACT FROM PUBLISHER]

The discipline of hydrology has a long history of research in the practical and theoretical aspects of scaling and scale issues, but little effort has been focused on hydrologists’ perception of the scale terms. What exactly do hydrologists mean when they use the terms “pore scale” or “regional scale”? The application of hydrological research requires clear communication, both within the discipline, and with a broader audience. Quantitative and qualitative data on hydrologists’ perceptions of scale were collected using voluntary written surveys and face-to-face interviews. The results suggest that most hydrologists do not consistently define scale terms in the literature, and that this is a minor impediment when interacting with other disciplines and stakeholders. Yet, surface water and groundwater hydrologists agree, within one to two orders of magnitude, on the length scale for most scale terms. Most respondents suggest that the hydrological community needs to better define the length scale of scale terms. In the short term, hydrologists could more frequently and consistently clarify their own length scales whenever a scale term is used. A common and consistent language of scale for hydrological researchers could better enable communication, research, teaching and outreach. EditorZ.W. Kundzewicz;Associate editorT. Wagener CitationGleeson, T. and Paszkowski, D., 2013. Perceptions of scale in hydrology: what do you mean by regional scale?Hydrological Sciences Journal, 59 (1), 99–107. [ABSTRACT FROM AUTHOR]

Information about the ZeroFlow workshop that was held in the U.S. and was organized by the International Association of Hydrological Sciences (IAHS) Decade for Prediction in Ungauged Basins (PUB) is presented. Topic includes temporary streams of the hydrological systems. The workshop featured several scientists and geologists including Jeff Woodword, John Lindsay and Howard Wheater.

L'objectif de ce travail est de fournir aux hydrologues travaillant sur l'Algérie du Nord un modèle numérique de terrain (MNT) permettant la mise en œuvre de méthodes d'estimation régionales de paramètres hydrologiques tels que les débits de crue instantanés décennaux ou les apports moyens annuels. Il doit permettre une détermination satisfaisante des contours des bassins versants et l'obtention de paramètres morphométriques comparables entre eux sur l'ensemble de la zone d'étude. Le MNT que nous proposons est un compromis entre des tailles de pixels petites donnant une bonne précision et des pixels plus grands permettant de couvrir uniformément la zone. Nous montrons que le MNT à la maille de 100 m est parfaitement adapté sous réserve de l'avoir préalablement corrigé manuellement dans les zones endoréiques et dans les zones relativement planes. Ce MNT permet de retrouver correctement les principaux paramètres morphométriques utilisés en hydrologie. Nous mettons donc à la disposition des hydrologues ce MNT à 100 m dans une projection Lambert bien adaptée aux besoins de l'hydrologie algérienne. Editeur Z.W. Kundzewicz Citation Rezak, S., Laborde, J.-P., et Errih, M., 2012. Validation d'un modèle numérique de terrain adapté à la modélisation hydrologique régionale sur l'Algérie du Nord. Hydrological Sciences Journal, 57 (5), 928–941. [ABSTRACT FROM AUTHOR]

Hydrologists responsible for flood management need real-time data in order to manage imminent or ongoing floods. In this paper, innovative methods for accessing hydrological data and their spatial visualization are introduced. A multitude of relevant real-time, forecast and historical information is provided in a single, self-updating hydrological map information system. The system consists of a central database and a cartographic user interface and provides harmonized and filtered data in the form of interactive, customizable maps. Maps may also be cross-referenced with historical maps or may be animated for improved comprehension and decision making. Emphasis is placed on the development of the hydrological real-time database that manages large amounts of spatial, temporal and attributive data. The paper focuses on the cartographic user interface, its functionality and the resulting interactive hydrological maps. Citation Lienert, C., Weingartner, R. & Hurni, L. (2011) An interactive, web-based, real-time hydrological map information system. Hydrol. Sci. J. 56(1), 1-16 [ABSTRACT FROM AUTHOR]

The novel research paradigm, dubbed the “court of miracles of hydrological modelling”, focuses on achieving scientific progress in circumstances which traditionally would be called model failures. Many of the associated modelling issues can be addressed systematically and coherently within the mathematical framework of Bayesian forecast-decision theory. Five of them are addressed herein: (a) choosing a criterion function for making rational decisions under uncertainty (a meta-decision problem); (b) modelling stochastic dependence between variates to quantify uncertainty and predict realizations; (c) fusing data from asymmetric samples to cope with unrepresentativeness of small samples and corruptive effects of outliers; (d) calibrating probabilistic predictions against a prior distribution; and (e) ordering predictors, or models, in terms of their informativeness (equivalently, in terms of their economic value to a decider). It is suggested that communication between hydrologists and deciders (planners, engineers, operators of hydrosystems) would benefit if hydrologists adopted, at least on some issues, the perspective of deciders, who must act in a timely and rational manner, and for whom hydrological estimates and predictions have economic consequences. Citation Krzysztofowicz, R. (2010) Decision criteria, data fusion and prediction calibration: a Bayesian approach. Hydrol. Sci. J. 55(6), 1033-1050. [ABSTRACT FROM AUTHOR]

In this article, we suggest that giving greater prominence to the analysis of failures and errors would more fruitfully advance the hydrological sciences. As widely recognised by philosophers of science, we can all learn from our mistakes, and errors can lead to discovery if they are properly diagnosed. However, failure stories are very seldom communicated and published, even though they represent the bulk of the results obtained by researchers and modellers. This article is the result of passionate discussions held in a workshop called the Court of Miracles of Hydrology held in Paris in June 2008. The participants had been invited to present their unpublished experience with what could be called monsters, anomalies, outliers and failures in their everyday practice of hydrology. The review of these studies clearly shows that in-depth analysis of these observations and results that deviate from the expected norm blazes a trail that can only lead to progress. Citation Andreassian, V., Perrin, C., Parent, E. & Bardossy, A. (2010) Editorial - The Court of Miracles of Hydrology: can failure stories contribute to hydrological science? Hydrol. Sci. J. 55(6), 849-856. [ABSTRACT FROM AUTHOR]

Providing the water needed to produce food for more than 9 billion people by 2050 seems simple: agriculture must produce more food with less water. However, three complex issues are involved: First, water, food production and rural development do not have a simple correlation. Second, there are interactions between processes at local, basin and global scales. Third, change involves people in complex networks of institutions. The Challenge Program on Water and Food brings together agriculturalists, hydrologists and development specialists in a global-to-local programme that focuses on change through institutions. We believe that this scale, complexity and involvement are necessary to deliver plausible change. [ABSTRACT FROM AUTHOR]

The purpose of this study is to develop a methodology that allows for an estimate of the hydroclimatic influence on an inland pond system on San Salvador, Bahamas. The methodology utilizes the Hydrologic Landscape Unit (HLU) model, a new conceptual model that offers hydrologists and water-resource managers more flexibility in representing the components of the unique and complex hydrologic systems of small carbonate islands. For this case study, a linear regression model was developed to empirically assess the HLU. This analysis separates tidal and climatic impacts on water levels of the pond and indicates that astronomical tides dominate, explaining 65% of the variance in pond water-level observations. Further, clusters of days with positive and negative outliers identified in the linear regression analysis were compared to precipitation events to determine response of water levels to climatic inputs. More than 78% of the days with positive outliers were associated with precipitation events and 83% of the days with negative outliers in Crescent Pond were explained by a lack of precipitation, signifying cumulative evaporation effects. Thus, while tidal variation is the principle forcing mechanism for Crescent Pond water-level variability, significant interaction between the atmosphere and the pond surface can be identified with this methodology at the daily to weekly time scale. Such a tool can be used by hydrologists and water-resource managers on small carbonate islands to assess the degree of freshwater input into inland water bodies and the appropriate time scale for potential freshwater harvest. [ABSTRACT FROM AUTHOR]

Solar engineers, architects, agriculturists, and hydrologists dealing with many applications of solar energy require a reasonably accurate knowledge about the availability of solar resources at any place. For this purpose, in the past, several empirical correlations have been developed in order to predict the solar radiation around the world. The present study, consisting of two parts, analyzes global solar radiation over the Central Anatolia Region (CAR) of Turkey along with its twelve provinces. Part 1 of this study includes the solar radiation models developed, while their statistical analysis is presented in Part 2. In the analysis, the data of the monthly average daily global solar radiation and sunshine duration measured by the Turkish State Meteorological Service in the period from January 1990 to December 1996 are used. Empirical models to estimate the monthly global solar radiation on a horizontal surface for each province are developed. The results obtained have indicated that the models developed here predict solar radiation reasonably well for future projections. [ABSTRACT FROM AUTHOR]

Writing in this journal, Amter and Ross (2001) have misrepresented the historical record of groundwater contamination due to chlorinated solvents. Contrary to their claims, the environmental community of groundwater hydrologists, environmental engineers, and regulators was caught by surprise in 1979-1981 by the discovery of the widespread contamination of groundwaters by dissolved chlorinated solvents and other toxic organic chemicals, a fact that was documented in the 1981 report by the Council on Environmental Quality. Given this ignorance and the guidance on the handling and disposal of spent chlorinated solvents from organizations such as the American Insurance Association as late as 1972, it is most likely that industry was equally uninformed about the threat posed by the intentional or unintentional releases of chlorinated solvents to the subsurface. Both the industrial and environmental communities had failed to undertake the necessary, continuing anticipatory research on the introduction of new chemicals prior to 1980. Serious misinterpretations of the historical record are due to Amter and Ross' misunderstanding of the wide array of nonchlorinated chemicals known as "solvents," of the meaning of the physical-chemical parameters describing immiscible liquids, and of the development of analytical methods for μg/L concentrations of volatile chlorinated organic compounds in groundwaters. The "conventional wisdom," which Amter and Ross find unacceptable, is conventional precisely because it is true to the historical record, to known principles of contaminant hydrogeology, and to the historical development of analytical chemistry. [ABSTRACT FROM AUTHOR]

The article focuses on the contaminated rain water in the U.S. Rain or snow that reaches the earth of the eastern part of the country is far from pure water and in relatively uncontaminated areas contains sea salts, sodium-calcium bicarbonates and sulfuric and nitric acids. According to D. W. Fisher, a hydrologist with the U.S. Geological Survey Water Resources Division, precipitation samples were gathered from a network of 52 collection stations, 17 scattered through the Northeast, 30 in North Carolina, and five in St. Thomas, Ontario.