Greening and Cooling Cities

Maintaining or expanding urban green spaces all-year-round introduces an uneasy tension between "greening cities" and "water saving" due to increased use of scarce blue water resources to maintain this greenness, particulary in dry regions or dry months of year.

Urban green spaces (UGS), like most managed land covers, are getting progressively affected by water scarcity and drought. Preserving, restoring and expanding green spaces in cities require sustainable management of green and blue water resources to fulfil evapotranspiration (ET) demand for green plant cover. The heterogeneity of UGS with high variation in their microclimates, vegetation species and water availability builds up the complexity of ET estimation. Often in‐situ approaches are not feasible or too expensive. We study the ET, water consumption and water footprint (WF) of urban greenery using different methods of remote sensing (RS), modelling and in-situ (ground-based) in different climates and geographical settings.

We have several ongoing collaborative projects on this topic listed below:

1. Assessing the spatio-temporal changes in the ET, greenness and water demand of urban greenery (2018-2023)

Dr. Hamideh Nouri has been working on the urban ET since 2010. In a series of related studies, the following tasks were set to improve the estimation of urban ET and assess the impact of spatial resolution of satellite images on estimating the greenness and water consumption of UGS:

Assessing the impact of spatial resolution of satellite images (WorldView2, Landsat and MODIS) on the estimation of ET and water consumption of UGS
Monitoring the greenness of UGS using vegetation indices (VIs) such as NDVI, EVI and EVI2
Assessing the long‐term intra‐ and inter‐annual variations of VIs and ET
Modelling urban ET using GIS/RS, eddy covariance (EC tower) and artificial intelligence
Comparing RS‐ET against the in-situ ET method

Members of the agronomy division involved in the study:
Dr. Hamideh Nouri

Students’ projects:
Ms Stenka Vulova (TU Berlin), PhD (2019-2022) – Heat and vapour fluxes of urban vegetation patterns – a remote sensing-based approach

2. Assessing water footprint of urban green spaces (2016-2022)

This research aims to estimate the green and blue water footprint of UGS to maintain and expand the green areas within a city and put the findings in the context of urban water budgeting. The water footprint (WF) of urban green spaces is defined as the volume of rainwater and irrigation water being consumed by these green spaces, i.e. the volume of water evaporating. This WF can be expressed as a volume per hectare or total volume when aggregated over the total area of green spaces. The amount of evaporated rainwater is called the green WF; the volume of evaporated irrigation water or evaporated groundwater from capillary rise is called the blue WF.

The novelty of this project is that it is the first study that applied the concept of WF in urban greenery. In this research, we focus on the blue water consumption of urban green spaces rather than on water abstracted to irrigate green spaces. We do this by using the water footprint, which measures both and distinguishes between the consumption of green and blue water resources.

Members of the agronomy division involved in the study:
Dr Hamideh Nouri, Prof. Stefan Siebert

Students’ projects:
Ms Julia Riama Silalahi, BSc student (2020-2021), The impact of climate on the water footprint of urban green spaces

3. The impact of local climate on the greenness and water demand of large urban green spaces (2019-2023)

Climate change and its impact on urban water cycles and water shortage are putting extra pressure on cities that are already vulnerable to water scarcity and drought. By recognising environmental-social-economic values of green spaces, many cities are searching for solutions to maintain and expand their green spaces in the context of a changing climate and more competition for water. In this project, we assess the impact of local climate on the greenness and the ET of UGS.

Members of the agronomy division involved in the study:
Dr Hamideh Nouri

Students’ projects:
Ms Jule Sophie Becker, BSc student (2020-2021),The impact of urban green spaces on cities and their inhabitants; benefits and services of different types of urban green spaces to alleviate challenges arise from ever-growing urbanization and climate change.

Collaborators:

U.S. Geological Survey: Dr Pamela Nagler
University of Arizona: Dr Kamel Didan, Dr Armando Barreto Munez
Isfahan Agricultural and Natural Resources Research Center of Iran: Dr. Sattar Chavoshi Borujeni
Monash University: Dr. Sina Alaghmand
Technische Universität Berlin: Ms. Stenka Vulova, Prof. Birgit Kleinschmit, Dr. Alby Rocha, Dr. Fred Meier
University of Twente: Prof. Arjen Hoekstra

Publications (2019 onward)

Journals:

Berger, M., Campos, J., Carolli, M., Dantas, I., Kosatica, E., Kramer, A., Mikosch, N., Nouri, H., Schlattmann, A., Schmidt, F., Scomberg, A. & E. Semmling, in press. Advancing the water footprint into an instrument to support achieving the SDGs – Recommendations from the Global Resource Water (GRoW) research initiative. Water Resource Management. DOI:10.1007/s11269-021-02784-9
Vulova, S., Meier, F., Rocha, A.D., Quanz, J.,Nouri, H., Kleinschmit, B. Modeling urban evapotranspiration using remote sensing, flux footprints, and artificial intelligence, Science of The Total Environment, 2021. https://doi.org/10.1016/j.scitotenv.2021.147293
Nouri, H., Nagler, P., Chavoshi Borujeni, S., Barreto Munez, A., Noori, B. Alaghmand, S. Galindo, A., Didan, K.; Effect of Spatial Resolution of Satellite Images on Estimating the Greenness and Evapotranspiration of Urban Green Spaces, Hydrological Processes, 2020. https://doi.org/10.1002/hyp.13790
Vulova, S., Meier, F., Fenner, D., Nouri, H., Kleinschmit, B. Summar nights in Berlin, Germany: Modelling air temperature spatially with crowd-sourced weather data, open-source geodata and machine learning. The IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing (JSTARS), 2020
Nouri, H., Chavoshi S., Hoekstra, A.Y. The blue water footprint of urban green spaces: An example for Adelaide, Australia, Landscape and Urban Planning, 2019, 190-103690

Conference contributions:

Nouri, H., Chavoshi Borujeni, S., Nagler, P., Barreto Munez, A., Didan, K, Hoekstra, A. Changes in the water footprint of urban green spaces over time. European Geoscience Union – EGU 2021, In Water and scociety-HS5.1 “Session Advancing in water footprint/water productivity.” Vienna, Austria. April 19-30, 202170391. EGU 2021
Nouri, H., Chavoshi Borujeni, S., Nagler, P., Barreto Munez, A., Didan, K, Spatio-temporal changes in water demand of urban greenery. European Geoscience Union – EGU 2021, In Hydrology-HS6 “Remote sensing and data assimilation, Session Remotely-sensed evapotranspiration.” Vienna, Austria. April 19-30, 2021. EGU 2021
Berger, M., Campos, J., Carolli, M., Dantas, I., Kosatica, E., Kramer, A., Mikosch, N., Nouri, H., Schlattmann, A., Schmidt, F., Scomberg, A., Semmling, E., Advancing the water footprint productivity. European Geoscience Union – EGU 2021, In Water and scociety-HS5.1 “Session Advancing in water footprint/water productivity.” Vienna, Austria. April 19-30, 2021. EGU 2021
Vulova, S., Meier, F., Rocha, A.D., Nouri, H., Kleinschmit, B. A data-driven approach to quantifying urban evapotranspiration using remote sensing, footprint modeling, and deep learning. European Geoscience Union – EGU 2021, In Hydrology-HS6 “Remote sensing and data assimilation, Session Remotely-sensed evapotranspiration.” Vienna, Austria. April 19-30, 2021. EGU 2021
Nouri, H., Chavoshi Borujeni, S., Nagler, P., A.Y. Hoekstra, A.Y., Estimation of evapotranspiration, water demand and water footprint of urban green spaces using ground-based and optical remote sensing techniques, EcoSummit 2020 - Session 044: Providing Solutions to a Current Environmental Problem Facing our Changing World: Improving Methods and Models Used to Measure and Scale Evapotranspiration (ET) to the Landscape Scale in Urban Regions, Catchments and Wetlands, EcoSummit 2020 (postpone to 14-18 June 2021, Gold Coast, Australia)
Nouri, H., Chavoshi Borujeni, S., Nagler, P., Barreto Munez, A., Didan, K.; The impact of local climate on the greenness and water demand of large urban green spaces, First International Conference on Urban Water Interfaces – UWI (22-24 September 2020, Berlin, Germany - online)
Nouri, H., Nagler, P., Chavoshi Borujeni, S., Barreto Munez, A., Didan, K., Alaghmand, S., Galindo, A., Impact of the spatial resolution of satellite images on the evapotranspiration estimation of urban green spaces using optical remote sensing, American Geoscience Union - AGU 2019 (9-13 December, San Francisco, USA)
Nouri, H., Nagler, P., Chavoshi Borujeni, S., Jarchow, C., Barreto Munez, A., Didan, K., Effects of spatial resolution of satellite images on the remote sensing-based evapotranspiration estimation of urban greenery, European Geoscience Union - EGU 2019 (8-13 April 2019, Vienna, Austria)