Recent news from WRMRG

Personnel changes

Nora Sillanpää, DSc (Tech), was appointed adjunct professor at the end of 2020. Nora is working mainly at Service Manager in the stormwater team of Sitowise’s Water Services. At Aalto, Nora is a part-time stormwater management professor.  

Postdoctoral researcher Hanne Laine-Kaulio moved to Academy of Finland in January 2021. Hanne is working as a Science advisor. 

Doctoral candidate Ambika Khadka will start working part time at ICEYE as a flood modelling hydrologist. She will continue to finish her PhD work at Aalto alongside with the new job. 

Eliisa Lotsari, PhD, was appointed assistant professor of Water engineering. Eliisa will start at her new position in August 2021. She will be joining our team from University of Eastern Finland where she still currently works as a university lecturer.  

Recent publications 

Äijö, H., Myllys, M., Sikkilä, M., Salo, H., Salla, A., Nurminen, J., Paasonen-Kivekäs, M., Koivusalo, H. 2021. Vesitalouden hallinta vesiensuojelussa (VesiHave). Loppuraportti 2021. Salaojjituksen tutkimusyhdistys ry:n tiedote 35.

The final report of the VesiHave (Use of water management in control of water pollution) is now published. The project was coordinated by Finnish Field Association (Salaojayhdistys) and it had both experimental field monitoring and mathematical modelling. Heidi Salo and Aleksi Salla simulated field hydrology in varying meteorological conditions in recent past (2015-2019) and far future (1970-2100) The project was funded by environmental ministry, Drainage foundation sr, Maa- ja vesitekniikan tuki ry and Sven Hallin research foundation. 

Caroppi, G., Västilä, K., Gualtieri, P., Järvelä, J., Giugni, M., & Rowiński, P. M. (2021). Comparison of Flexible and Rigid Vegetation Induced Shear Layers in Partly Vegetated Channels. Water Resources Research, e2020WR028243.

Key implications of using natural-like vegetation in the simulation of vegetated flows (from Caroppi et al., 2021). 

Conference participation 

McS Aleksi Salla attended EGU 2021 Virtual conference. Aleksi had a pico presentation about his master’s thesis study. The presentation was held in session “Hydrological processes in agricultural lands under changing environments” on Monday, 26 April 2021, 09:30 CEST.  

Posted by Gerardo Caroppi

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My thesis – Controlled drainage in future climate

-Aleksi Salla

In the beginning of 2020, I started my master’s thesis process under the supervision and advisement of prof Harri Koivusalo and Heidi Salo from Water and Environmental engineering (Aalto University) and Olle Häggblom from Finnish Field Drainage Association. My thesis was part of the VesiHave project, which aims to improve crop productivity and reduce harmful environmental impacts of cultivation by field water management. As the title suggests, my job was to simulate the effects of future climate on the hydrological processes of an experimental field located in Sievi, North Ostrobothnia, Finland. The objective of the thesis was to assess how the controlled drainage affects the field hydrology (especially water table depths and runoffs) and how these impacts might change under future climate conditions. Controlled drainage is a method, where drainage efficiency can be controlled to some extent. This is typically done with control wells, where the drain outlet can be blocked to prevent drain discharge up to some desirable elevation of the groundwater table. The aim is to maintain sufficient soil moisture for the crop and reduce the environmental impacts of drain discharge while enabling sufficient drainage when needed (e.g. when heavy machinery is operated on the field).

In the thesis process, I enjoyed the fact that I was able to work with things relatively new to me, but in which I had gained some interest in my previous studies, such as modeling and programming. In the process, I also obtained more insight into climate change, cultivation and time series analysis as well as working with large quantities of data.

I used a three-dimensional, spatially distributed and process based FLUSH model to simulate four drainage scenarios in two future climatic conditions (best case and worst case scenarios). The simulation input included hourly meteorological data and drain control parameters for years 1970-2100. It came out to be a large dataset with 1147560 rows. The Aalto desktop didn’t even begin to simulate the whole 131 year period, but fortunately I was able to use the CSC supercomputers to run the simulations (IT Center for Science Ltd.). With whopping 1.8 petaflops, so they say, the runs took approximately 35 hours (triple checking the input every time would’ve really saved some time). The output data was even larger with >50 columns of hydrological variables for each scenario, so with the internet connection I had, downloading the data took some time. Then importing the data into a python platform took some time. Of course visually presenting simulation results into  beautiful graphs took some time. With all that waiting, shifting between tasks is a skill to be learned for sure.

I worked at home most of the year as most of you due to the pandemic restrictions. No commuting, peaceful solitude in a cosy environment, doing whatever you want on breaks. “What a luxury!”, I thought at first. It turned out it wasn’t. Spending almost all the time at home, lines between work time and free time tended to get really blurry (“I can finish this later” am I right?), and I ended up feeling like having less free time than before. But never I felt like I was alone with my thesis process, thanks to the people I worked with!

In November 2020 my thesis was approved, and currently I am working on publishing the study as a peer reviewed journal article, hopefully to be published some day! Below you can see an example of my results (Figure 1). The graph shows growing season groundwater table depth distributions for four consecutive time intervals between 1970-2100. Orange is conventional  subsurface drainage and blue is controlled drainage (Scenario Säätö 1: reduced drainage efficiency during growing season and from October to March. Scenario Säätö 2: reduced drainage efficiency during growing season and from October to November.) RCP 8.5 is the high-emission scenario and RCP 2.6 is the low-emission scenario. Two things the graph shows: 1) the efficacy of controlled drainage in reducing deep groundwater tables remains similar during the 21st century in both emission scenarios and 2) reducing the drain intensity over winter has a notable impact on summer groundwater levels (Säätö 1 vs. Säätö 2).

Figure 1. Simulated groundwater table depths as frequency distributions during different time intervals (S0–S3) (Salla, 2020).


Salla, A. 2020. Säätösalaojitus tulevaisuuden ilmastoskenaarioissa (Eng. Controlled drainage in future climate scenarios). Master’s thesis. Aalto University.

Posted by Ambika Khadka

Ambika is a doctoral researcher focusing on urban stormwater management using Nature-based solutions (NBSs). Her research approach is numerical modeling of water flow on surface and in pipe networks to quantify effects of NBSs on overall hydrological behavior of stormwater in urban catchments.
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Dealing with complexity at the Environmental Hydraulics Lab

Simplification is a crucial and sometimes unavoidable step for the physical description of reality. In the study and modelling of flow in natural watercourses, significant simplifications have been traditionally introduced as to handle the complexity deriving from the presence of vegetation. In many watercourses, flow and vegetation mutually interact resulting in complex flow patterns that affect the mass and energy transport processes. Accurately modelling such interaction is therefore of crucial importance for properly addressing issues like flood risk management, transport of sediments, erosion, and transport and fate of pollutants.

 Vegetation is a fundamental component of hydro-ecosystems (photo by Gerardo Caroppi).

Faced with the challenging task of representing vegetation in laboratory and numerical models, researchers have mainly simulated vegetation as simple rigid cylinders. Such representation neglects important flow-influencing mechanisms exhibited by natural vegetation and is quite far from reality for many ecologically-important environmental settings. Floodplains and river margins are generally populated by a variety of different species ranging from grasses to shrubs and trees. Such vegetation presents a peculiar structure with branches and leaves and, under the flow forcing, bends and moves, giving rise to a complex flow-vegetation interaction.

A laboratory setup at the EHL (photo by Gerardo Caroppi).

At the Environmental Hydraulics Lab (EHL) we investigate how to effectively translate the complexity of natural hydro-environmental settings into laboratory and numerical models of vegetated flows. In our experiments, carried out in laboratory controlled conditions, vegetation is represented by natural-like plants that closely reproduce the hydrodynamic behavior of vegetation commonly found in riparian areas. By introducing controlled elements of realism in the vegetation representation we aim at improving the understanding of hydrodynamic processes occurring in natural systems.

My research at the EHL started between 2017 and 2018, during my PhD. As a visiting student from University of Naples, I spent a semester (including an exceptionally snowy winter) at Aalto University within the water resources management and environmental hydraulics research team. From that visiting period, my collaboration with the team has become progressively more intense till the starting of my postdoc here at Aalto University.

Gerardo Caroppi

Posted by Camilla Tuomela

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Webinar on Land use and water resources management in a changing environment

(In Finnish: Maankäyttö ja vesitalouden hallinta muuttuvassa ympäristössä)

Already a traditional seminar, held in every second year, was this time organized as a webinar. This was the fourth time Drainage Foundation sr, Maa- ja vesitekniikan tuki ry, BSAG and Finnish Field Drainage Association invited speakers to talk to and discuss with stakeholder groups. Previous seminars were focusing on agricultural water management and climate change, but this time other land use areas were recognized already in the event name. It is an aim to consider agricultural and forest water management together rather than individuals. Same methods can be applied in both areas and in hybrid areas that contain forest and agriculture.

This seminar was organized as a webinar due to the corona situation. However, this enabled larger audience group to follow the webinar. Over 400 people registered beforehand and the webinar was attended by 200-300 listeners at the same time.

A wide range of experts and researchers from different fields were invited to speak at the seminar. After the opening words by Gustav Rehnberg, Elsi Katainen spoke about the new directions and future decisions of the EU’s agricultural and forestry policy in relation to carbon sinks and changes in subsidies. Research professor Heikki Lehtonen (Natural Resources Institute Finland) continued the seminar by talking about the future of Finnish agriculture, how agricultural practices could develop in the future, in order to meet the current environmental emission targets. This was followed by a farmer-oriented speech by Jyrki Wallin, new Executive Director of MTK (Central Union of Agricultural Producers and Forest Owners). The presentation demonstrated interesting results from a survey that showed farmers ’views on many important topics, such as climate change.

Before the lunch break, Ville Keskisarja presented the new strategy for agriculture and forestry water management and Eliisa Malin gave inspiration for land owners to start applying light methods for improving soil wellbeing and conditions for better crop growth.

After the break, the seminar continued with agricultural nutrient loads. Sirkka Tattari from Finnish Environmeltal Institute spoke about monitoring nutrient loads and how the loads have been developing so far. Hannu Marttila continued with peatland water management and described their current study in Oulu University. A new experimental field had been implemented in Ruukki and there will be both monitoring and modelling to study peatland water management in different conditions. Throughout the day, there had been information on controlled drainage method and now Heidi Salo explained the benefits of controlled drainage in future climate conditions. Heidi is working in Aalto University Water Resources Management and Environmental Hydraulics research team. The last presentation was about forests, when Paavo Ojanen from the University of Helsinki spoke about the environmental effects of forest drainage.

The webinar can be viewed as a recording:

There will be a theme number 1/2021 of the Vesitalous magazine “Land use and water management in a changing environment”. The magazine will be published in early 2021 in January-February.

Posted by Heidi Salo

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The Hulevesi2020-seminar was organized online

The stormwater seminar Hulevesi2020 was organized online 23.9.2020 by the Urban stormwater division of the Finnish Water Association. The seminar gathered over 300 participants and brought together experts working with stormwater in different sectors. The purpose of the seminar was to promote practical implementation of current knowledge, share experiences within the stormwater field and enable discussion and networking. The change to an online seminar created challenges for the networking part, but the chat-function enabled questions and discussion between participants and presenters. The seminar was mainly held in Finnish, but also included a few presentations in English.

The seminar day included 20 presentations divided into six sessions and five stormwater related topics:
–  Planning and practices, I and II
–  Contaminants
–  Heavy rainfall, floods and modelling
–  Stormwater management and modelling
–  Multidisciplinary and -objective planning of stormwater management

The presentation materials and a recording of the seminar (morning and afternoon separately) are published online and freely available.

From our research group several people were involved in the seminar and the doctoral candidates Ambika Khadka and Camilla Tuomela each held a presentation in the stormwater management and modelling session. Ambika Khadka’s presentation (in English) title was “Stormflow against streamflow –can storage capacity ensure performance efficiency and maintenance of pre-development flow regime?”. Camilla Tuomela’s presentation (in Finnish) topic was impacts of stormwater management structures and climate change on runoff and loading in a residential catchment.

Posted by Camilla Tuomela

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Infrastructure walk in Otaniemi

Otaniemi, a suburban campus surrounded by a long coastline, is facing challenges of urban densification in the recent years. Currently, approximately 70% of Otaniemi is impervious including streets, rooftops, and parking lots. The future development plans for Otaniemi suggest a continuous increase in the local population, students, and workers, which will lead to the expansion of the urban scene. The increased construction will add pressure to the outdated conventional stormwater system on the campus. This will result in adverse effects such as pluvial flooding due to stormwater overflows.

However, there is an enormous potential in using nature-based solutions (NBS) to minimize the adverse effects of urbanization.  NBS can reduce the water volume and peak time of stormwater overflow, restore the natural water cycle as well as add biodiversity to the campus landscape. They can further improve the attractiveness of the campus.

Lin Chun made her master’s thesis to explore the benefits of using nature-based solutions in stormwater management on the campus in order to reduce pressure on the existing stormwater drainage network. Low impact development measures such as green roofs, impervious pavements, and vegetated swales were explored. The thesis was conducted in collaboration with ACRE, the Aalto University Campus & Real Estate, and NODUS, the sustainable design research group in the Department of Design, Aalto University.

The results of Chun’s thesis were communicated in the Infrastructure walk in Otaniemi to discuss sustainable stormwater management on campusThe walk was part of the Designs for a Cooler Planet event for Helsinki Design Week 2020. It was hosted by Eeva Berglund and Idil Gaziulusoy from NODUS, and joined by Ville Jokela from ACRE, and Chun Lin, Dr. Juha Järvelä, and Professor Harri Koivusalo from the Water Resources Management and Environmental Hydraulics research team.

Walking and talking together, experts and users alike learn from each other and from the surroundings. An ancient learning practice, walking projects in recent years have drawn attention to public discomforts with mainstream development(source:

The infrastructure walk started from Väre building, walking through the old and new area of Otaniemi, and ended in Ossilamppi.

Infrastructure walk route 

The rainy weather on that day provided an opportunity to showcase the stormwater issues and management using nature-based solutions in action. The professionals engaged in an intensive exchange of their views from the perspectives of stormwater management, service design, and land and infrastructure management. This type of walk is a good way to connect professionals in different fields as well as everyday users of infrastructures. It provided educational yet mutual communication practices.

Stormwater starting to accumulate in the street during rain 

Ossilamppi pond 

Roadside swale in action 

Rain garden in action




Environmental Hydraulics Lab (  Environmental Hydraulics Lab is currently working on improving stormwater management on campus.


Posted by Ambika Khadka

Ambika is a doctoral researcher focusing on urban stormwater management using Nature-based solutions (NBSs). Her research approach is numerical modeling of water flow on surface and in pipe networks to quantify effects of NBSs on overall hydrological behavior of stormwater in urban catchments.
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Research team introduction

We would like to embark on the journey of blogging by introducing Water Resources Management and Environmental Hydraulics research team at Aalto University. Be ready to get to know this group of vibrant doctoral students, post-doctoral researchers and teaching staffs and learn about their research.

Harri Koivusalo ( is a Professor of Water resources engineering. He works with students, postdocs, and faculty in the field of hydrology and water resources management. He teaches two master’s courses: Hydrological modelling (WAT-E2030) and Surface Water Resources (WAT-E2040).




Teemu Kokkonen ( is a Senior University Lecturer at the Aalto University School of Engineering. Dr. Kokkonen’s research interests are in the field of Urban hydrology, Hydrological modelling and Geospatial computing. His courses are Applied hydrology (YYT-C2005, in Finnish), and Groundwater Hydrology (WAT-E2010).



Juha Järvelä ( is a Staff Scientist at the Aalto University School of Engineering. His main tasks are hydro-environmental research, development of water engineering hybrid research infrastructure in the newly modernized Aalto Environmental Hydraulics Laboratory, doctoral candidate training, and teaching MSc and BSc students.

Dr. Järvelä’s research interests are in the field of environmental hydraulics and ecohydraulics. His scientific contributions deal with flow-vegetation-sediment interactions, with expertise in experimental research with natural plants. Most recently, his research has focused on improving hydraulic 1/2/3D models based on physically based characterisation of complex vegetation using novel remote sensing methods.


Kaisa Västilä ( is a Postdoctoral Researcher funded by the Academy of Finland. She investigates nature-based solutions for river and agricultural water management. Her expertise is on the physical flow and transport processes in such complex vegetated settings. Her current research aims at improving the understanding on the nutrient retention and processing on man-made floodplains of compound (two-stage) channels, and on integrating findings of the laboratory and field studies into hydrodynamic modelling. The knowledge produced supports the optimal design and maintenance of sustainable river engineering solutions. Her current collaborators include Korea Institute of Civil Engineering and Building Technology, Institute of Geophysics of the Polish Academy of Sciences, Warsaw University of Life Sciences, Deltares, University of Sheffield, University of Helsinki and Finnish Environment Institute (SYKE). At Aalto, she works mainly working with Juha Järvelä, Walter Box and Gerardo Caroppi. She also participates in teaching at some courses.

P.S. Her research has also made her an expert on vegetative decorations! She have had the pleasure to use her working time for shopping at interior design sections of major department stores (to find artificial plants to simulate natural floodplain vegetation) and for familiarizing herself with the properties of willows (if you are interested they have great willows for weaving at Ritobäcken field site!).

Gerardo Caroppi ( is a Postdoctoral Researcher at the Aalto University School of Engineering. His main research interests are in the field of environtmental hydraulics with a focus on the interaction of flow with aquatic and riparian vegetation. His research aims at improving the understanding of hydrodynamic processes in critically-important ecosystems.




Heidi Salo ( is working as a Postdoctoral Researcher in the research team and her research focus is in agricultural water management. She started working in the group in 2013 when she started her master’s thesis. She continued with her doctoral studies. Her main research method is mathematical modelling that she uses for simulating water flow and solute transport in soil. She also participates in teaching, mostly by working as an instructor for bachelor and master’s thesis.




Ambika Khadka ( is a doctoral candidate in the research team. Her research field is urban hydrology and her research focuses on urban hydrological modeling to quantify the effects of Nature-based Solutions on the urban hydrological processes. She also assists in teaching, i.e. Urban hydrology week in Hydrological Modelling and Groundwater Hydrology, and as an instructor to master’s thesis. She is supervised by Teemu Kokkonen and Harri Koivusalo.

Outside of work, she likes to be out in nature, which also means play-acting real-life Minecraft with her daughter.



Maija Jylhä-Ollila is a doctoral candidate in the research team. Her PhD studies is about the long-term impact of managed aquifer recharge on groundwater quality. She is supervised by Hanne and Harri. Besides this, she also works as team manager of the groundwater team at Ramboll. She is not seen often in Otaniemi but is remotely active to participate in events organized by the university.




Camilla Tuomela ( is a doctoral candidate in the research team. Her research topic is urban runoff management and modelling of stormwater quantity and quality. Her main objective is to identify and evaluate water quality patterns and pollutant transport mechanisms from source areas to receiving urban streams. She is supervised by Harri Koivusalo and advised by Nora Sillanpää (Sitowise).




Ville Lindgren ( is a doctoral candidate in the research team. His research topic is rainfall simulations and modelling. He works closely with his advisors Teemu Kokkonen (Aalto) and Tero Niemi (Finnish Meteorological Institute). Harri Koivusalo is his supervising professor. He has not participated in teaching yet but is interested in doing so in future.

Outside of work he likes to spend the most time with his daughter, and the remaining for other hobbies, i.e. football and outdoor activities as well as eSports.



Posted by Camilla Tuomela

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This will be a blog for research communication of the Water Resources Management and Environmental Hydraulics Research Team at Aalto University School of Engineering.

The aims and scope of the research team are to:

  • promote sustainable use of water and advance the assessment and prediction of the state of the water environment
  • measure and quantify changes in water and the water environment caused by anthropogenic activities in both empirical and laboratory settings
  • develop computational hydrology and hydraulics applications, ecohydraulics, nature-based solutions and basin-scale process examination – the watershed basin is our key unit, enabling the study of the effects of land cover and sub-processes related to precipitation, evapotranspiration, water storage and runoff development

In this area, the main topics of our work are:

  • ecohydraulics and nature-based solutions
  • water in cities
  • water in agricultural areas
  • water in forests

Posted by Camilla Tuomela

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  • Presentation

    This is a blog for research communication of the Water Resources Management and Environmental Hydraulics Research Team at Aalto University School of Engineering.
    We will write about ongoing research projects, events, publications and present group members.

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