Hilary Mcmillan

Hilary Mcmillan
San Diego State University | SDSU · Department of Geography

About

95
Publications
22,131
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
4,022
Citations
Additional affiliations

Publications

Publications (95)
Article
Full-text available
Dominant processes in a watershed are those that most strongly control hydrologic function and response. Estimating dominant processes enables hydrologists to design physically realistic streamflow generation models, design management interventions, and understand how climate and landscape features control hydrologic function. A recent approach to...
Article
Full-text available
Soil moisture signatures provide a promising solution to overcome the difficulty of evaluating soil moisture dynamics in hydrologic models. Soil moisture signatures are metrics that quantify the dynamic aspects of soil moisture timeseries and enable process‐based model evaluations. To date, soil moisture signatures have been tested only under limit...
Article
Full-text available
This paper presents a taxonomy (hierarchical organization) of hydrological processes; specifically, runoff generation processes in natural watersheds. Over 130 process names were extracted from a literature review of papers describing experimental watersheds, perceptual models, and runoff processes in a range of hydro‐climatic environments. Process...
Preprint
Full-text available
Soil moisture signatures provide a promising solution to overcome the difficulty of evaluating soil moisture dynamics in hydrologic models. Soil moisture signatures are metrics that quantify the dynamic aspects of soil moisture timeseries and enable process-based model evaluations. To date, soil moisture signatures have been tested only under limit...
Article
Full-text available
The link between landscape properties and hydrological functioning is the very foundation of hydrological sciences. The fundamental perception that landscape organisation and its hydrological and biogeochemical processes co-develop is often discussed. However, different landscape characteristics and hydrological processes interact in complex ways....
Preprint
This paper presents a taxonomy (hierarchical organization) of hydrological processes; specifically, runoff generation processes in natural watersheds. Over 120 process names were extracted from a literature review of papers describing experimental watersheds, perceptual models, and runoff processes in a range of hydro-climatic environments. Process...
Article
The study had two objectives; (1) Substitute National Water Model’s (NWM) runoff calculation with a conceptual hydrologic model (TOPography‐based hydrological MODEL [TOPMODEL]) to simplify the model structure and resolve potential drawbacks of applying NWM in headwater catchments. (2) Investigate how varying the coupling interface (location of coup...
Preprint
Soil moisture signatures provide a promising solution to overcome the difficulty of evaluating soil moisture dynamics in hydrologic models. Soil moisture signatures are metrics that represent catchment dynamics extracted from time series of data and enable process-based model evaluations. To date, soil moisture signatures have been tested only unde...
Article
Full-text available
Study region In this study, we use stable isotopes of water to quantify the flow pathways delivering water to the tributaries, mainstem river and groundwater basin underlying urban San Diego. Information about sources of stormflow and recharge are necessary to maintain the health of waterways and aquifers, but studies of these processes are scarce...
Article
Full-text available
A catchment's hydrological response is controlled by climatic forcing and by the landscape through which water moves. Yet when we compare large samples of catchments, we often find climate to be the only good predictor of the hydrological response and a lot of variability is left unexplained. This contradicts extensive evidence from field and regio...
Article
Full-text available
We present a Matlab toolbox to calculate hydrologic signatures, which are metrics that quantify streamflow dynamics. Signatures are widely used for catchment characterisation, hydrologic model evaluation, and assessment of instream habitat, but standardisation across applications and advice on signature selection is lacking. The toolbox provides ac...
Article
Soil moisture is a key modifier of runoff generation from rainfall excess, including during extreme precipitation events associated with Atmospheric Rivers (ARs). This paper presents a new, publicly available dataset from a soil moisture monitoring network in Northern California's Russian River Basin, designed to assess soil moisture controls on ru...
Article
Hydrologic signatures are quantitative metrics or indices that describe statistical or dynamical properties of hydrologic data series, primarily streamflow. Hydrologic signatures were first used in eco‐hydrology to assess alterations in flow regime, and have since seen wide uptake across a variety of hydrological fields. Their applications include...
Preprint
Full-text available
Hydrologic signatures are quantitative metrics or indices that describe statistical or dynamical properties of hydrologic data series, primarily streamflow. Hydrologic signatures were first used in eco-hydrology to assess alterations in flow regime, and have since seen wide uptake across a variety of hydrological fields. Their applications include...
Article
Hydrological signatures that represent snow processes are valuable to gain insights into snow accumulation and snow melt dynamics. We investigated 5 snow signatures. Considering inter‐annual average of each calendar day, two slopes derived from the relation between streamflow and air temperature for different periods and streamflow peak maxima are...
Article
Full-text available
Increased climate variability is driving changes in water storage across the contiguous United States (CONUS). Observational estimates of these storage changes are important for validation of hydrological models and predicting future water availability. We estimate CONUS terrestrial water storage anomalies (TWSA) from 2007–2017 using Global Positio...
Article
Full-text available
Hydrologic signatures are metrics that quantify aspects of streamflow response. Linking signatures to underlying processes enables multiple applications such as selecting hydrologic model structure, analysing hydrologic change, making predictions in ungauged basins, and classifying watershed function. However, many lists of hydrologic signatures ar...
Article
Soil moisture is an important variable in hydrological studies, but has been little used for model evaluation due to its high sensitivity to local conditions. We explore the possibility to derive hydrological signatures from soil moisture data that could overcome this limitation and be helpful for model evaluation. A set of 8 hydrological signature...
Poster
Full-text available
Rainfall-runoff event delineation is typically performed manually, which is effort- and resource-intensive and impedes comparisons of hydrologic response characteristics across scales and environments. Here the goal was to leverage a new, automated rainfall-runoff event delineation tool to achieve such a comparison. Two objectives were pursued: 1)...
Article
Full-text available
Hydrologic data are at the core of our understanding of physical hydrologic processes, our simulation models and forecasts of water resources and hazards, and our monitoring of water quantity and quality. However, hydrologic data are subject to multiple sources of uncertainty that can introduce bias and error into our analyses and decision‐making i...
Article
Streamflow time series are commonly derived from stage-discharge rating curves, but the uncertainty of the rating curve and resulting streamflow series are poorly understood. While different methods to quantify uncertainty in the stage-discharge relationship exist, there is limited understanding of how uncertainty estimates differ between methods d...
Poster
Full-text available
Hyetograph-hydrograph analysis, notably following manual rainfall-runoff event delineation, is commonly performed to establish characteristics of rainfall-runoff relationships, in terms of timing (e.g., response lag) and magnitude (e.g., runoff ratio). To date, manual event delineation proved to be effort-intensive, therefore impeding comparative s...
Article
Full-text available
Stage measurement errors are generally overlooked when streamflow time series are derived from uncertain rating curves. We introduce an original method for propagating stage uncertainties due to two types of stage measurement errors: (i) errors of the stage read during the gauging; (ii) systematic and non-systematic (independent) errors of the reco...
Article
Streamflow data are used for important environmental and economic decisions, such as specifying and regulating minimum flows, managing water supplies, and planning for flood hazards. Despite significant uncertainty in most flow data, the flow series for these applications are often communicated and used without uncertainty information. In this comm...
Poster
Full-text available
A hydrologic threshold is a critical point in time when runoff behavior rapidly changes, often in response to the activation of specific storage-driven or intensity-driven processes. Hydrologic thresholds can be viewed as characteristic signatures of hydrosystems, which makes them useful for site comparison as long as their presence (or lack thereo...
Article
Most rivers worldwide have a strong interaction with groundwater when they leave the mountains and flow over alluvial plains before flowing into the seas or disappearing in the deserts, and in New Zealand, typically rivers lose water to the groundwater in the upper plains and generally gain water from the groundwater in the lower plains. Aiming at...
Article
Nationwide predictions of flow time-series are valuable for development of policies relating to environmental flows, calculating reliability of supply to water users, or assessing risk of floods or droughts. This breadth of model utility is possible because various hydrological signatures can be derived from simulated flow time-series. However, pro...
Article
Full-text available
This paper describes the first version of a stand-alone runoff routing tool, mizuRoute. The mizuRoute tool post-processes runoff outputs from any distributed hydrologic model or land surface model to produce spatially distributed streamflow at various spatial scales from headwater basins to continental-wide river systems. The tool can utilize both...
Article
Full-text available
This paper describes implementation of an operational flow forecasting system for New Zealand that couples a high-resolution (1.5 km) weather forecast model to a hydrological model. The impact of the high resolution weather forecast is tested for two large storms in a case study catchment where convective storms and orographic rains – only modelled...
Article
The clustering of catchments has been important for prediction in ungauged basins, model parameterization and watershed development and management. The aim of this study is to explore a new measure of similarity among catchments, using a data depth function and comparing it with catchment clustering indices based on flow and physical characteristic...
Article
Irrigation using groundwater in Canterbury, New Zealand, is reaching sustainable limits and to assist with water allocation a better understanding of groundwater recharge from irrigated agriculture is required. To help characterise groundwater recharge from irrigated pasture, three sets of three drainage lysimeters were installed in three irrigated...
Article
Full-text available
In 2013, the IAHS launched the hydrological decade 2013–2022 with the theme “Panta Rhei: Change in Hydrology and Society”. The decade recognises the urgency of hydrological research to understand and predict the interactions of society and water, to support sustainable water resource use under changing climatic and environmental conditions. This pa...
Article
Root zone storage capacity (Sr) is an important variable for hydrology and climate studies, as it strongly influences the hydrological functioning of a catchment and, via evaporation, the local climate. Despite its importance, it remains difficult to obtain a well-founded catchment representative estimate. This study tests the hypothesis that veget...
Article
Full-text available
Reliable information about hydrological behavior is needed for water-resource management and scientific investigations. Hydrological signatures quantify catchment behavior as index values, and can be predicted for ungauged catchments using a regionalization procedure. The prediction reliability is affected by data uncertainties for the gauged catch...
Article
Full-text available
This paper describes the first version of a stand-alone runoff routing tool, mizuRoute, which post-processes runoff outputs from any distributed hydrologic model or land surface model to produce spatially distributed streamflow at various spatial scales from headwater basins to continental-wide river systems. The tool can utilize both traditional g...
Article
In the past, hydrologic modeling of surface water resources has mainly focused on simulating the hydrologic cycle at local to regional catchment modeling domains. There now exists a level of maturity among the catchment, global water security, and land surface modeling communities such that these communities are converging toward continental domain...
Article
Full-text available
Information about rainfall–runoff processes is essential for hydrological analyses, modelling and water-management applications. A hydrological, or diagnostic, signature quantifies such information from observed data as an index value. Signatures are widely used, including for catchment classification, model calibration and change detection. Uncert...
Article
Information about rainfall–runoff processes is essential for hydrological analyses, modelling and water-management applications. A hydrological, or diagnostic, signature quantifies such information from observed data as an index value. Signatures are widely used, including for catchment classification, model calibration and change detection. Uncert...
Article
Full-text available
Hydrological processes, including runoff generation, depend on the distribution of water in a catchment, which varies in space and time. This paper presents experimental results from a headwater research catchment in New Zealand, where we made distributed measurements of streamflow, soil moisture and groundwater levels, sampling across a range of a...
Article
Full-text available
This paper explores the use of entropy-based measures in catchment hydrology, and provides an importance-weighted numerical descriptor of the flow duration curve. Although entropy theory is being applied in a wide spectrum of areas (including environmental and water resources), artefacts arising from the discrete, under-sampled and uncertain nature...
Article
River discharge values, estimated using a rating curve, are subject to both random and epistemic errors. We present a new likelihood function, the ‘Voting Point’ likelihood that accounts for both error types, and enables generation of multiple possible multi-segment power law rating curve samples that aim to represent the total uncertainty. The rat...
Article
Full-text available
Parameter estimation for hydrological models is complicated for many reasons, one of which is the arbitrary emphasis placed, by most traditional measures of fit, on various magnitudes of the model residuals. Recent research has called for the development of robust diagnostic measures that provide insights into which model structural components and/...
Article
In this paper, we develop diagnostic methods to assess spatial variability in hydrological processes, particularly those relevant to catchment modelling. We target a range of catchment responses, including runoff volume, runoff timing, storage–discharge relationships, and threshold responses to rainfall and soil moisture. The diagnostics allow us t...
Article
Full-text available
Hydrological processes, including runoff generation, depend on the distribution of water in a catchment, which varies in space and time. This paper presents experimental results from a headwater research catchment in New Zealand, where we made distributed measurements of streamflow, soil moisture and groundwater levels, sampling across a range of a...
Article
Full-text available
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 syst...
Article
Full-text available
Quantifying future increases in sea level around New Zealand arising from climate change is a key factor for determining decisions on adaptation, yet most projections are expressed in terms of a global-mean rise in sea level. The work presented here makes use of the data from the Atmosphere-Ocean General Circulation Models (AOGCM) used in the 4th I...
Article
Lumped hydrological models are often faster, easier to implement and less sensitive to equifinality than distributed models. Lumped models are however subject to a loss of spatial information and process representation. Landscape classification in different hydrological units might be a solution to retain maximum simplicity while taking into accoun...
Article
We report recent progress on a long-term hydrological modelling project whose goal is to make reliable estimates of all water fluxes and storages of New Zealand, and reliable estimates of potential changes in those water resources. This is an ambitious scientific project, with many practical implications for water use and water planning. The model...
Article
Hydrologists increasingly agree that a single hydrological model structure is unlikely to be suitable for all catchments: instead, models should be selected according to characteristics of the catchment. Our challenge is to determine how to select the most appropriate model structure. This complex question requires that we use observed data to infe...
Article
Highlights ► We developed DIE algorithm to differentiate cases of interpolation/extrapolation. ► The algorithm is based on the location of new data in relation to a convex hull. ► We used DIE algorithm to improve the predictive uncertainty of the forecast flow. ► The concepts of the paper can applied in an operational setting.
Article
Full-text available
This paper describes the design and use of a recursive ensemble Kalman filter (REnKF) to assimilate streamflow data in an operational flow forecasting system of seven catchments in New Zealand. The REnKF iteratively updates past and present model states (soil water, aquifer and surface storages), with lags up to the concentration time of the catchm...
Article
This review and commentary sets out the need for authoritative and concise information on the expected error distributions and magnitudes in observational data. We discuss the necessary components of a benchmark of dominant data uncertainties and the recent developments in hydrology which increase the need for such guidance. We initiate the creatio...
Article
Full-text available
Calibration of rainfall-runoff models is made complicated by uncertainties in data, and by the arbitrary emphasis placed on various magnitudes of the model residuals by most traditional measures of fit. Current research highlights the importance of driving model identification by assimilating information from the data. In this paper, we evaluate th...
Article
This paper uses soil moisture data from 17 recording sensors within the 50 km2 Mahurangi catchment in New Zealand to determine how measured variability in soil moisture affects simulations of drainage in a typical lumped conceptual model. The data show that variability smoothes the simulated field capacity threshold such that a proportion of the ca...
Article
Full-text available
This paper describes the use of the Retrospective Ensemble Kalman Filter (REnKF) to assimilate streamflow data in an operational flow forecasting system of seven catchments in New Zealand. The REnKF updates past and present model states (soil water, aquifer and surface storages), with lags up to the concentration time of the catchment, to improve m...
Article
In this paper we explore the use of time-variable tracer data as a complementary tool for model structure evaluation. We augment the modular rainfall-runoff modeling framework FUSE (Framework for Understanding Structural Errors) with the ability to track the age distribution of water in all model stores and fluxes. We therefore gain the novel abili...
Article
Hydrological Models are simplifications and theoretical approximations of complex natural phenomena. Hence, they cannot predict perfectly what happen in natural systems. There are several reasons; some of the main reasons are error in the input data, imperfect model structure, insufficient information for parameter identification etc. The identific...
Article
In this paper we explore the potential for an ensemble of hydrological model structures coupled to Regional Climate Models to predict current and future changes in river flows. We develop this approach for a large number of catchments in the UK using the FUSE (Framework for Understanding Structural Errors) modelling framework. This ensemble of mode...
Article
This paper presents good practice methods for flood risk assessment under climate change in urban areas of New Zealand, following techniques selected from the "Impacts of Climate Change on Urban Infrastructure and the Built Environment Toolbox" (see the first paper in this special issue and NIWA, MWH, GNS and BRANZ, 2012). A case study evaluating f...
Article
This presentation describes the use of tracer dynamics as an orthogonal data source to assist the choice of model structure within a multi-model framework. Tracers are a valuable model diagnostic tool because they provide information about integrated catchment response from an alternative perspective to the commonly-used rainfall and runoff dynamic...
Article
This paper presents an investigation of rainfall error models used in hydrological model calibration and prediction. Traditional calibration methods assume input error to be negligible: an assumption which can lead to bias in parameter estimation and compromise model predictions. In response, a growing number of studies now specify an error model f...
Article
The current generation of hydrological models has been widely criticized for their inability to adequately simulate hydrological processes. In this study, we evaluate competing model representations of hydrological processes with respect to their capability to simulate observed processes in the Mahurangi River basin in Northland, New Zealand. In th...
Article
Hydrological scientists develop perceptual models of the catchments they study, using field measurements and observations to build an understanding of the dominant processes controlling the hydrological response. However, conceptual and numerical models used to simulate catchment behaviour often fail to take advantage of this knowledge. It is commo...