Let me guess from which city in the world you are reading this post: Lima, Lahore or Louisville? It might be that you are modelling one of these rivers: Nile, Rhine or Lena? Or studying the Caribbean Sea, the Arabian Sea or the Caspian Sea?
The country you live might be Uganda, Philippines or maybe Iceland and your home continent could well be Europe, Latin America or even Antarctica. I assume you are certainly from this world, not outer space! :), and the reason why I wanted to take you on a “world” tour is to highlight the importance of scales and context in how knowledge, thus perception, is shaped.
In the search for answers for known unknowns, and also unknown unknowns, a fresh and open mind is required to be able to take in all the inspiration offered by observations, data and theories. Moreover, scientific thinking is equally enriched by a bird’s-eye view.
Knowledge production and networking opportunities have improved significantly in the last century, and even more so since 1990s. There are thousands of research papers available in the literature, and the speed of both research and publishing is utterly increasing.
Most often than not, reading the literature can feel endless, like looking up into the night sky and wondering just how many stars are there in the universe! However, a greater challenge remains for scientists, especially when the pace of scientific publishing continues to rise.
Review papers as tools for research integration and synthesis
One of the biggest concerns of a scientist might well be keeping up with the literature and maintaining a research vision. Questions like “what are the research gaps and priorities?”, “What are the research challenges and opportunities?” constantly pop up in the minds of many. A healthy option for researchers to keep up to date with the literature (without information overload), while maintaining a bird’s-eye view to be able to better understand research gaps and priorities, is reading review papers.
Research integration and synthesis is one of the core activities of the scientific process, and review papers are the perfect tools for it! They present “new conceptual frameworks, reveal inconsistencies in the extant body of research, synthesize diverse results, and generally give other scholars a ‘state-of-the-art’ snapshot of a domain” (Palmatier et al., 2018).
Original research articles typically cover background, hypothesis/objectives of the study, methods, interpretation of findings, and discussion of possible implications. Review papers, on the other hand, do not offer new methodologies or present new case studies. It is important that a review paper give an overall synthesis and perspective on a specific research topic and a particular context. A review paper’s objective (and its contributions) can significantly vary. However, some common objectives can be found (Palmatier et al., 2018):
- Resolve definitional ambiguities and outline the scope of the topic,
- Provide an integrated, synthesized overview of the current state of knowledge,
- Identify inconsistencies in prior results and potential explanations,
- Evaluate existing methodological approaches and unique insights,
- Develop conceptual frameworks to reconcile and extend past research,
- Describe research insights, existing gaps, and future research directions.
Reading a review paper is somewhat similar to getting a nice bouquet of flowers at a flower shop. The florist uses their floral design skill to create a magical beauty (a feast for the eyes!) that will inspire your soul. Likewise, the authors of a review paper put their best into this motivational and creative effort. Recently, I accepted the challenge for writing a review paper on clustering algorithms in hydrology and I realize that writing a review paper is not an easy task. It is a huge responsibility!
Recipes on how to write a review paper exist
Scholarly journals have various kinds of scientific publications – research articles that report on original research being the most common type. Besides, review papers and perspective/opinion pieces are considered as an article type by many journals, including those in hydrological sciences. There are also journals which are dedicated to publishing only review papers, e.g.: Wiley Interdisciplinary Reviews: Water (aka WIREs Water), Reviews of Geophysics or Environmental Research Reviews.
Each journal has its own policy on review papers, yet the common practice for many journals is that they are solicited by the editors (to experienced researchers). For unsolicited submissions, potential authors are required to contact the journal Editor-in-Chief where they justify the need for their review idea.
Specific guidelines on what should be in a review paper and the required methodology can be found on a journal’s website. One can also check the general guidelines provided by publishers like Taylor & Francis and Elsevier. The length of a review paper usually varies depending on the subject area, selected journal, and most importantly, the type of review paper. There are different types of review papers. A classification can be made with respect to (Mayer, 2009; Snyder, 2019; Palmatier et al., 2018):
- the paper’s objective (status-quo, history, issue, theory/model),
- the paper’s focus theme (domain-based, theory-based, method-based), or
- the paper’s methodological approach (systematic, semi-systematic, integrative).
What are the review methodologies?
Conducting reviews include both narrative and/or quantitative (i.e., systematic, meta-analytic reviews) approaches. A narrative review is not as detailed and rigorous as a systematic review, and focuses on a particular field or topic rather than a well-defined research question. A systematic review, however, aims to offer comprehensive background for theory development and testing by adopting a transparent methodology for scientific reproducibility so that the bias in exhaustive literature searches is minimized (Linnenluecke et al., 2019).
Meta-analysis is a kind of systematic review where the quantitative findings across reviewed studies is statistically combined in order to obtain new insights. If you are planning on conducting a systematic review you might want to first read the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Existing guidelines for conducting a literature review is listed in Snyder (2019). I would also recommend the review paper by Grant et al. (2009) where 14 most common review types are compared and the need for an internationally agreed set of discrete, coherent and mutually exclusive review types is discussed.
Review papers are not a shortcut to have that literature review you are supposed to do on your own
Reading individual articles in your field with a focus on your research interests is absolutely necessary. Nothing can replace the unique benefits of this task. Review papers are rather valuable tools that enable readers to get an overview on a mature (or expanding) topic within a wider context while engaging in critical evaluation and reflective discussion.
Just like looking at these lovely photos of flower bouquets, reading review papers can help you find the inspiration that you have been longing for. There is a bouquet (oops! a review paper) for every taste, that’s for sure!
Review papers in Hydrology
In hydrological sciences, review papers are popular too. Both the authors and the readership appreciates the benefits of review papers. It is highly probable that everyone reading this post had read at least one review article on a hydrological topic. If so, you can share your most recent read in the comments!
The number and scope of review papers has increased substantially (personal observation). For example, just in Hydrology and Earth System Sciences alone 69 papers classified as review article are published since 2011; and 28 papers (7 opinion, 8 overview, 13 advanced review) are published only this year in WIREs Water (i.e. Volume 8). Note that both numbers are as of June 1st, 2021.
I have been collecting review (or overview) papers over the last seven years (since 2014 – when I started my PhD studies). I try my best to keep my collection as diverse as possible in terms of topics so that I can develop a basic level of understanding on each topic while embracing multi-/inter-/transdisciplinarity of hydrological sciences. At the end of this post I am sharing a list of review papers that gives a quite comprehensive overview of the hydrology literature (as of June 1st, 2021). The list is shaped mainly by my research interests and learning needs, and thus it is not exhaustive.
I consider these review papers as chapters of a hydrology book that would be my life-time bedside book – a wonderful book that one can refer to whenever I need to explore further an idea or to learn about a new topic to support my research vision with new insights. I can’t help but wonder how many of these review papers are actually open access. The overview and discussion presented in these papers can be of interest to non-academic hydrologists as well as policy makers. Overall, I believe that such review papers have great value for strengthening the science- policy-practice interface.
You can also share your favourite review paper(s), which helped expand your knowledge and inspired your research, by adding a comment under this post. It might be also that you authored a review article yourself and want to share that too!
Hydrology for generations Z and Alpha
It is interesting to note that there is a considerable boom in the number (and topical variety) of review papers in 2020 and (first half of) 2021. It seems that the hydrological sciences community is marking the end of the first 1/5th period of the 21st century by publishing review papers.
An exciting period is awaiting us for the next 100 years. New theories, new methods, innovative approaches, and new observational data… The babies of the last two decades (generation Z and generation Alpha) – mostly children of Millennials – are coming to transform the hydrological sciences landscape! Some of them have already joined the hydrology community, e.g. current BSc and MSc students in environmental and water sciences. In order for them to create new science, they will need to know enough about the current knowledge and practice.
Luckily some of the newbie hydrologists are already concerned by the power of water. Have you watched the water-inspired interval act by the host country, the Netherlands, during the first semi-final of the Eurovision Song Contest 2021? It was held in Rotterdam, May 18-22. The act is named ‘The Power of Water’. The song “Sweet Water” by Davina Michelle tells the story of the unique relationship between the Netherlands and water. If you haven’t, check it out (for lyrics click).
Generation Z and Alpha is born to a world of water extremes, so much that a musical show with the theme of hydrological extremes is staged at the Eurovision 2021! The world definitely needs more hydrologists!!! Hence, these review papers are the diamonds of academic publishing for their initiation in hydrological sciences!
Snyder, H. (2019). Literature review as a research methodology: An overview and guidelines. Journal of Business Research, 104, 333-339. https://doi.org/10.1016/j.jbusres.2019.07.039
Palmatier, R. W., Houston, M. B., & Hulland, J. (2018). Review articles: Purpose, process, and structure. Journal of the Academy of Marketing Science, 46, 1–5. https://doi.org/10.1007/s11747-017-0563-4
Linnenluecke, M. K., Marrone, M., & Singh, A. K. (2020). Conducting systematic literature reviews and bibliometric analyses. Australian Journal of Management, 45(2), 175-194. https://doi.org/10.1177%2F0312896219877678
Grant, M. J., & Booth, A. (2009). A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26(2), 91-108. https://doi.org/10.1111/j.1471-1842.2009.00848.x
https://www.editage.com/insights/a-young-researchers-guide-to-a-systematic-review (Accessed on 02 June 2021)
The list of 151 review papers collected can be downloaded here.
* In chronological order by year (and by topic within a year):
- scale issues in hydrological modelling: Blöschl and Sivapalan, 1995
- baseflow recession analysis: Tallaksen, 1995
- neural networks for the prediction and forecasting of water resources variables: Maier and Dandy, 2000
- hydrological modelling using artificial neural networks (ANN): Dawson and Wilby, 2001
- input variable selection for ANN: Bowden et al., 2005
- model evaluation for hydrological models: Moriasi et al., 2007
- catchment classification and hydrologic similarity: Wagener et al., 2007
- dominant processes, model simplification and classification framework: Sivakumar, 2008
- self-organizing map in water resources: Kalteh et al., 2008
- ensemble flood forecasting: Cloke and Pappenberger, 2010
- multi-objective calibration in hydrological modelling: Efstratiadis and Koutsoyiannis, 2010
- ANN development methods for prediction water resource variables: Maier et al., 2010
- input variable selection for ANN: May et al., 2011
- self-organizing map in ecological sciences: Chon, 2011
- advances in flash flood forecasting: Hapuarachchi et al., 2011
- hydrological impacts of imperviousness in urban catchments: Jacobson, 2011
- entropy for hydrologic synthesis: Singh, 2011
- hydrologic synthesis: Thompson et al., 2011
- hydrologic classification for ecohydrologists: Olden et al., 2011
- regionalisation for continuous streamflow simulation: He et al., 2011
- regionalization methods for streamflow prediction in ungauged basins: Razavi and Coulibaly, 2013
- predictions in ungauged basins (IAHS PUB): Hrachowitz et al., 2013
- change in hydrology and society (IAHS Panta Rhei): Montanari et al., 2013
- wavelet transform applications in hydrology time series analysis: Sang, 2013
- ASCAT soil moisture product: Wagner et al., 2013
- citizen science in hydrology and water resources: Buytaert et al., 2014
- challenges of operational river forecasting: Pagano et al., 2014
- evolutionary algorithms in water resources: Maier et al., 2014
- support vector machines: Raghavendra and Deka, 2014
- hybrid wavelet–artificial intelligence models: Nourani et al., 2014
- large-sample hydrology: a need to balance depth with breadth: Gupta et al., 2014
- catchment hydrology and predictions under change: Ehret et al., 2014
- karstic water resources: Hartmann et al., 2014
- hydrological drought: van Loon, 2015
- remote sensing of droughts: AghaKouchak et al., 2015
- artificial intelligence and streamflow forecasting: Yaseen et al., 2015
- physically-based modeling in catchment hydrology: Paniconi and Putti, 2015
- hydrological processes and Earth System Models: Clark et al., 2015
- global hydrology: Bierkens, 2015
- global hydrological models: Sood and Smakhtin, 2015
- water management: Casgrove and Loucks, 2015
- hydrology education: Ruddell and Wagener, 2015
- legacy and perspectives for the science of hydrology: Montanari et al., 2015
- discovery science for hydrological hypotheses: Burt and McDonnell, 2015
- time scale interactions and the coevolution of humans and water: Sivapalan and Blöschl, 2015
- catchment classification framework: Sivakumar et al., 2015
- hydrological modelling with the Budyko framework: Wang et al., 2016
- large-scale hydrological models for (continental) operational flood forecasting: Kauffeldt et al., 2016
- continental and global scale flood forecasting systems: Emerton et al., 2016
- data-driven modelling and socio-hydrology: Mount et al., 2016
- transdisciplinarity of water research: Krueger et al., 2016
- interdisciplinarity of water science: Vogel et al., 2015
- urban development and hydrology: McGrane, 2016
- rainfall variability and hydrological response in urban areas: Cristiano et al., 2017
- monitoring network design for rainfall and streamflow: Chacon-Hurtado et al., 2017
- entropy applications to water monitoring network design: Keum et al., 2017
- soft computing based hybrid models in hydrological variables modelling: Fahimi et al., 2017
- heterogeneity measures in hydrological frequency analysis: Requena et al., 2017
- soil moisture for hydrological applications: Brocca et al., 2017
- applications of ASCAT soil moisture products: Brocca et al., 2017
- terrestrial diatoms as tracers in catchment hydrology: Pfister et al., 2017
- integrated water assessment and modelling: Zare et al., 2017
- bayesian flood forecasting methods: Han and Coulibaly, 2017
- hydrology and social sciences: Seidl and Barthel, 2017
- hydrological data biases and errors: Wilby et al., 2017
- process-based hydrologic models: Clark et al., 2017
- large-scale controls of the surface water balance over land:Padrón et al., 2017
- hydrological understanding and its evolution: Sivapalan and Blöschl, 2017
- interdisciplinary evolution of water resource science: McCurley and Jawitz, 2017
- transformation of hydrologic science: Sivapalan, 2018
- 100 years of progress in hydrology: Peters-Lidard et al., 2018
- Global Flood Partnership (GFP) and operational flood risk reduction: Alfieri et al., 2018
- flood forecasting techniques: Jain et al., 2018
- flood prediction using machine learning: Mosavi et al., 2018
- forest ecology and machine learning: Liu et al., 2018
- machine learning classification in remote sensing: Maxwell et al., 2018
- deep learning in water resources: Shen, 2018
- citizen science for hydrological risk reduction and resilience: Paul et al., 2018
- crowdsourcing methods for data collection in geophysics: Zheng et al., 2018
- citizen observations and flood modelling: Assumpção et al., 2018
- participatory early warning systems and citizen science: Marchezini et al., 2018
- innovation and multidisciplinarity for hydrological observations (IAHS MOXXI): Tauro et al., 2018
- freshwater plastic pollution: Blettler et al., 2018
- shallow subsurface of karst systems: Berthelin and Hartmann, 2018
- stable water isotopes and snow hydrological processes: Beria et al., 2018
- global isotope hydrogeology: Jasechko, 2019
- bayesian modelling for hydrologists: Höge et al., 2019
- random forests for water scientists: Tyralis et al., 2019
- extreme learning machine model for river flow forecasting: Yaseen et al., 2019
- using R in hydrology: Slater et al., 2019
- large sample hydrology: Addor et al., 2019
- estimation of uncertainty in flood forecasts: Boelee et al., 2019
- 23 unsolved problems in hydrology – UPH: Blösch et al., 2019
- global hydrology research agenda for 2030s: Wilby, 2019
- hydraulics in the 21st century: McDowell et al., 2019
- socio-hydrology and SDGs: Di Baldassarre et al., 2019
- citizen science in hydrological monitoring and ecosystem services management: Njue et al., 2019
- citizen science and SDGs: Fritz et al., 2019
- observational methods for hydrological sciences: Beven et al., 2020
- innovation and hydrological processes: Bracken et al., 2020
- historical development of rainfall-runoff modelling: Peel and McMahon, 2020
- ensemble flood forecasting: Wu et al., 2020
- impact forecasting for natural hazards: Merz et al., 2020
- flood resilience: McClymont et al., 2020
- water cycle modifications and Earth system resilience: Gleeson et al., 2020
- citizen science for hydrological challenges: Nardi et al., 2020
- exploratory modelling and coupled human-natural system: Moallemi et al., 2020
- social-environmental extremes: Balch et al., 2020
- agent-based models for flood risk modelling: Aerts, 2020
- agent-based modelling and flood risk management: Zhuo and Han, 2020
- groundwater in high mountain environments: Somers and McKenzie, 2020
- remote sensing and water security: Chawla et al., 2020
- remote sensing applications in agriculture for food security: Karthikeyan et al., 2020
- compound weather and climate events: Zscheischler et al., 2020
- integrated urban hydrometeorological, climate and environmental services: Grimmond et al., 2020
- global datasets for studying the water-society interplay: Lindersson et al., 2020
- open water balance for network design and data analysis: Kampf et al., 2020
- measurements and modelling in ecohydrology: Guswa et al., 2020
- rainfall input and urban rainfall models: Hu et al., 2020
- remote sensing applications with Google Earth Engine: Amani et al., 2020
- flowing wells: Jiang et al., 2020
- in situ measurements of soil and plant water isotopes: Beyer et al., 2020
- ice jam modelling with artificial intelligence: Madaeni, 2020
- rainfall and flood frequency analysis using stochastic storm transposition: Wright et al., 2020
- fuzzy logic applications in hydrology: Kambalimath and Deka, 2020
- neurocomputing in surface water hydrology and hydraulics: Zounemat-Kermani et al., 2020
- hydropower optimization research with meta-heuristic approaches: Azad et al., 2020
- probable maximum precipitation: Salas et al., 2020
- remote sensing of river discharge: Gleason and Durand, 2020
- satellite soil moisture applications: Peng et al., 2021
- hydrologic signatures: McMillan, 2021
- hydrology of non-perennial rivers and streams: Shanafield et al., 2021
- hydrological model uncertainties: Moges et al., 2021
- operational surface water flood forecasting: Speight et al., 2021
- urban surface water flood modelling: Guo et al., 2021
- catchment water quality monitoring approaches: O’Grady et al., 2021
- soil erosion modelling: Borrelli et al., 2021
- baseflow and transmission loss: McMahon and Nathan, 2021
- regionalization of hydrological modelling for predictions ungauged basins: Guo et al., 2021
- flood and drought modelling: Brunner et al., 2021
- nonstationary weather and water extremes: Slater et al., 2021 (accepted preprint)
- water resource management: Lv et al., 2021
- agricultural water quality management: Saia et al., 2021
- flood risk analysis methods: Diaconu et al., 2021
- flood source area identification: Singh et al., 2021
- flood vulnerability indices: Moreira et al., 2021
- flood management and computer vision: Iqbal et al., 2021
- coastal storm analysis: Martzikos et al., 2021
- resilience research on climate change: Ossewaarde et al., 2021
- resilience and water–energy–food nexus: Hogeboom et al., 2021
- green roofs for urban water-energy-food-ecosystem nexus: Cristiano et al., 2021
Check also these:
- WRR Special Issue on the occasion of 50th Anniversary of Water Resources Research, 2015
- Wiley Encyclopedia of Hydrological Sciences, 2005
- Guide to Hydrological Practices: WMO, 2008
Edited by Maria-Helena Ramos