Project

Back to overview

Evaporation suppression from water reservoirs using floating covers: scientific basis and design considerations

English title Evaporation suppression from water reservoirs using floating covers: scientific basis and design considerations
Applicant Or Dani
Number 172493
Funding scheme Project funding (Div. I-III)
Research institution Institut für Biogeochemie und Schadstoffdynamik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Hydrology, Limnology, Glaciology
Start/End 01.08.2017 - 30.09.2020
Approved amount 207'007.00
Show all

All Disciplines (2)

Discipline
Hydrology, Limnology, Glaciology
Civil Engineering

Keywords (3)

evaporation suppression; surface-atmosphere coupling; floating cover

Lay Summary (German)

Lead
Um Verdunstungsverluste aus Wasserreservoirs in trockenen Gebieten zu minimieren, können Schwimmkörper auf der Wasseroberfläche verteilt werden. Wir erforschen, wie die Schwimmkörper für verschiedene klimatische Bedingungen beschaffen sein müssen, um die Verdunstungsverluste zu minimieren.
Lay summary

Um die Wasserversorgung in ariden Gebieten zu gewährleisten, wird Wasser häufig während den nassen Monaten in Wasserreservoirs gespeichert. Beträchtliche Mengen des gespeicherten Wassers können in heissen Monaten aber verdunsten und können nicht mehr genutzt werden. Um diese Wasserverdunstung aus Reservoirs zu vermeiden, gibt es zwar verschiedene technische Möglichkeiten, die Lösung einer Abdeckung durch Schwimmkörper scheint aber besonders effizient. Dazu werden viele schwimmende Objekte (oft Kugel- oder Linsenförmig) auf der Wasseroberfläche verteilt, um den Anteil der unbedeckten Wasserfläche zu minimieren. Zwar ist das Wirkungsprinzip der Abdeckung durch Schwimmkörper (Reduzierung der verdunstenden Wasseroberfläche) sehr direkt und einfach, die genauere Quantifizierung der Verdunstungsverluste wird aber durch folgende physikalische Sachverhalte erschwert: (1) zwischen den sich berührenden Schwimmkörpern hat es kleine Lücken, aus denen überproportional viel Wasser verdunsten kann (über jedem kleinen Loch hat es einen grossen Bereich trockener Luft, in dem sich Wasserdampf verteilen kann); (2) die Farbe und Beschaffenheit der Schwimmkörper verändert den Energiehaushalt des Reservoirs und es besteht die Möglichkeit, dass Energie durch die Schwimmkörper nicht zurückgestrahlt sondern aufgenommen wird und so die Temperatur und die Verdunstungsrate erhöht. Diese Vorgänge werden in diesem Projekt nun erstmals systematisch und unter Feldbedingungen quantifiziert. Das Ziel der Projektes besteht darin, Richtlinien auszuarbeiten, wie Schwimmkörper konstruiert werden müssen, um für ein bestimmtes Klima die Verdunstungsverluste zu minimieren.

Direct link to Lay Summary Last update: 25.07.2017

Responsible applicant and co-applicants

Employees

Project partner

Publications

Publication
Distribution of small seasonal reservoirs in semi-arid regions and associated evaporative losses
Mady Bassem, Lehmann Peter, Gorelick Steven M, Or Dani (2020), Distribution of small seasonal reservoirs in semi-arid regions and associated evaporative losses, in Environmental Research Communications, 2(6), 061002-061002.
Evaporation suppression from water bodies using floating covers: laboratory studies of cover type, wind and radiation effects
Lehmann Peter, Aminzadeh Milad, Or Dani (2019), Evaporation suppression from water bodies using floating covers: laboratory studies of cover type, wind and radiation effects, in Water Resources Research, 2018WR0244-2018WR0244.
Evaporation suppression and energy balance of water reservoirs covered with self-assembling floating elements
Aminzadeh Milad, Lehmann Peter, Or Dani (2018), Evaporation suppression and energy balance of water reservoirs covered with self-assembling floating elements, in Hydrology and Earth System Sciences, 22(7), 4015-4032.

Datasets

Small Reservoirs

Author Mady, Bassem
Persistent Identifier (PID) c258f1894088eaff7ff0
Repository Figshare


Suppression

Author Lehmann, Peter
Persistent Identifier (PID) https://figshare.com/articles/Suppression/7378469
Repository Figshare


Collaboration

Group / person Country
Types of collaboration
Stanford University, CA United States of America (North America)
- Publication

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
AGU Fall meeting 2019 Poster Evaporation suppression from water reservoirs using floating covers - insights from a field study 09.12.2019 Washington DC, United States of America Or Dani; Mady Bassem Mansour Abdelhady Youssef; Lehmann Peter;
EGU General Assembly 2019 Poster Floating covers for evaporation suppression from small reservoirs - global survey of feasibility and water saving potential 07.04.2019 Vienna, Austria Mady Bassem Mansour Abdelhady Youssef; Lehmann Peter; Or Dani;
EGU General Assembly 2018 Poster Evaporation suppression from water reservoirs using floating covers – preliminary results from field experiments 08.04.2018 Vienna, Austria Lehmann Peter; Mady Bassem Mansour Abdelhady Youssef; Or Dani;
EGU General Assembly 2018 Talk given at a conference How many small water reservoirs are there? A global survey using multi spectral Imagery 08.04.2018 Vienna, Austria Lehmann Peter; Or Dani; Mady Bassem Mansour Abdelhady Youssef;


Associated projects

Number Title Start Funding scheme
135077 Evaporation from terrestrial surfaces - linking pore scale phenomena with landscape processes 01.08.2011 Project funding (Div. I-III)
182734 Deciphering mechanisms of soil bacterial community assembly under changing hydration regimes 01.01.2019 Project funding (Div. I-III)
113676 Evaporation from porous media - microscale study of the dynamics and morphology of drying fronts 01.01.2007 Project funding (Div. I-III)

Abstract

The competition over dwindling fresh water resources is expected to intensify with projected increase in human population and expansion of irrigated land, and with changes in precipitation and drought patterns. Water storage in reservoirs will likely to increase to mitigate seasonal shortages due to precipitation variability, and to meet water needs for increased food production. By some estimates up to half of stored water in reservoirs is lost to evaporation thereby exacerbating the water scarcity problem. Interests in suppressing evaporation have led to an upsurge in the use of floating covers over water reservoirs (e.g. Los Angeles 2015 and elsewhere), yet the selection and implementation of such measures remain largely empirical. Recent studies have shown that evaporation suppression is highly nonlinear and depends on the properties of the covers and elements geometry. Our previous studies have linked basic diffusive interactions between pores (gaps in a cover) and boundary layer characteristics (wind-surface interactions) with evaporation rates and energy partitioning over surfaces. We propose to build on these principles and develop a mechanistic framework for evaporation suppression using self-assembling floating covers considering evaporation and energy balance of different cover designs. We envision incorporation of ecological consideration in terms of gas exchange, light penetration, and thermal regimes in a water body. Selected cover designs will be tested in a wind tunnel at the lab scale (1-2 square meters basins), and at pilot scale experiments (10-100 square meters) in dry regions (Nevada, USA and Shahrood, IRAN) to test model predictions and cover performance. The study will provide a much-needed scientific basis for an important water resource protection strategy in regions that suffer from chronic water scarcity and requiring more storage due to climate change.
-