Water conservation | EPFL Graph Search

Water conservation includes all the policies, strategies and activities to sustainably manage the natural resource of fresh water, to protect the hydrosphere, and to meet the current and future human demand (thus avoiding water scarcity). Population, household size and growth and affluence all affect how much water is used. Factors such as climate change have increased pressures on natural water resources especially in manufacturing and agricultural irrigation. Many countries have already implemented policies aimed at water conservation, with much success. The key activities to conserve water are as follows: any beneficial reduction in water loss, use and waste of resources, avoiding any damage to water quality; and improving water management practices that reduce the use or enhance the beneficial use of water. Technology solutions exist for households, commercial and agricultural applications. Water conservation progra

Optimization of drip irrigation using a sensor network in Sahel Region (Burkina Faso) - Analysis of soil water and plant dynamics in the framework of project Info4Dourou 2.0

Tom Müller

The research project Info4Dourou 2.0 's main goal is to improve agriculture in semi-arid regions by developing a support system that optimizes agricultural production and water consumption based on continuous soil humidity measurements using a sensor network. In this context, the main purpose of the study was to give more scientific support to the agronomic model on which the sensor network is based. In particular the research aims at understanding the soil water and plant dynamics in order to give recommendations on the system design. The main feature of the system is to indicate when irrigation must be triggered and in which soil moisture conditions. The thesis developed a numerical model based on the software HYDRUS 2D to acquire a precise knowledge on the soil water dynamics and was calibrated and coupled with field experiments on two vegetable crops of eggplant and cabbage in Burkina Faso using drip kit irrigation systems. A great focus was given on the plant response to different irrigation schedules and to water stress, considering aerial biomass development, root distribution and final yields. Water stress was linked to continuous measurements of the soil matrix potential at different depth and locations. The field experiments showed that a daily irrigation frequency resulted to better canopy development during the first part of the growth but that great water savings are possible by optimizing the schedule. Water stress was difficult to track precisely by following daily sap flow behaviour which suggested that plant stress occurs before transpiration reduction, especially when biomass is building up. The adaptability of the root distribution was demonstrated and was clearly correlated with the wetted zone which depended on the irrigation schedule. From the numerical model, it was shown that using one sensor at a depth of about 10 cm was most appropriate in order to pilot irrigation during the whole crop growth. The analysis showed that most of the water savings could be achieved at relatively high threshold values and that low thresholds mainly resulted to transpiration reduction which was not advisable. A threshold of -20 kPa was proposed for the beginning of the growth stage which then decreases to a value of -50 kPa at full canopy development. These thresholds are believed to be adequate for most vegetable crops since they allow keeping the soil matrix potential in the root zone at values that are tolerated by most plants. An analysis of the influence of the soil texture also showed that similar values seem to perform well for most soils, if assuming an adaptation of the root distribution to the wetted zone. The study focused mainly on water stress but more research could be done on the impact of the irrigation system on nutrients availability for example.

2015

Occupant satisfaction in non-well and well certified office buildings

Serra Yildirim

People spend around 90 percent of their time indoors (home, oce, transportation) in developed countries [1]. This means a long exposure to indoor conditions that have higher concentrations of pollutants compared to outdoors. This exposure can aect the well-being, performance and health of the occupants, making indoor environments even more important. On the other hand, the design and operation of buildings need energy. Following the oil crisis in 1974, building envelopes were aimed to be more air tight to decrease the energy consumption for heating and cooling. In addition to the economic costs, according to International Energy Agency (IEA), building sector is responsible for almost forty percent of energy-related CO2 emissions worldwide [2]. The Intergovernmental Panel on Climate Change (IPCC) report by UN body stresses the importance of evolving to greater sustainability in land, energy, buildings and cities to reach the reduced CO2 levels in order to limit global warming by 1.5°C [3]. With increasing concerns about environment and global warming, decreasing the energy intensity of the building operations became a goal. As a result, creating comfortable indoor environments with less energy demand became a hot topic and green building certications were promoted. While environmental concerns led to focusing on the energy and water conservation, the indoor environmental quality and health aspects of green buildings were less recognized [4]. The green building certications had their sections related to occupant health and well-being, but recently there has been a prioritization of human health relative to the energy consumption. The companies understand that the cost of workers is higher than the cost of energy. In a company, 90% of operating costs is salary/benets of sta, 9% is rental costs and only 1% is energy [5]. A study done in Harvard School of Public Health shows that elevated CO2 levels result in a 50% decrease in cognitive function [6]. In addition, a lack of fresh air is shown to cause 35% of total absenteeism in a company [7]. In relation to these aspects, WELL certication is a new rating system that focuses on occupant health and wellness through design and operation of buildings. However, no studies were done so far to see its eectiveness. This study was designed to address this knowledge gap. It is the rst cohort study done in WELL buildings. The project aims to compare the satisfaction levels, productivity and SBS symptoms with an online indoor environmental quality (IEQ) survey done in non-WELL and WELL buildings.

2020

Impact de l'exploitation des alpages sur la qualité des eaux

Agricultural fertiliser (farmyard manure), covers partially the nutrient elements demand of the vegetation cover. However, its application is difficult as regards the unknown concentration of fertilising elements contained and their biological availability for the plants, the important volumetric masses to manage and the general uneven land application. An inaccurate management of farmyard manure may cause groundwater pollutions with sometimes serious consequences, especially in the case of karst aquifers. The objective of this research was to specify various aspects of the farmyard manure cycle. It consists of three major parts: a general study of the difficulties related to the farmyard manure management in mountainous regions with the aim to provide practical recommendations to reduce the risk of groundwater contaminations, the evaluation of an alternative method of pig farming in liberty the study of the impacts of agricultural activities on the surface- and groundwater quality. Based on the analysed farmyard manure managements, the following practical recommendations have been made: split up the land application, but concentrate the input of nutrient elements in spring, during the period of plant growth. For sanitary reasons, a delay of at least 1 month has to be respected between the last land application and the beginning of pasture; collect in adequate installations all agricultural effluents which potentially cause water pollution, except if they are spread out immediately. minimise the production of fertiliser by the following two possibilities: infiltrate low contaminated waste water (from the roof, spring, eventually from the farm) reduce the time the animals stay in the stable. An alternative method of pig farming in liberty has been tested in the field. 25 pigs have been raised on a field of ca. 2 ha, representing a density of 0.71 LiveStock Unit/ha/y, respectively 0.18 LSU/ha/m during 4 months. Amongst others, the study has considered the impacts of pig pasture on the environment (vegetation cover, soil) and the animals health. The most important impact is in fact the destruction of the vegetation cover, with its direct repercussions on the botanical diversity and the concentration of nutrients in the soil. The experiment has made evident the importance to keep the vegetation cover intact, in order to adsorb the nutrient elements in the manure. An advantageous method to reduce the impacts on the vegetation cover is to equip the pigs with nose-rings. It is furthermore necessary to altemate the pasture parks in order to enable the vegetation to recover (2 to 3 different parks). The important impacts observed around the pig feeding through can be avoided by two ways: first, by changing the throughs placement during the pasture period or second, by the construction of a concrete place and the collection of the manure in the slurry pit. For the pasture of pigs in liberty one has to chose grasslands with thick soils of good quality but avoid oligotrophic ones. Cattle sheds and feeding through have to be placed in a manner to favour a maximum dispersion of the animals. Two hydrogeological observation networks, composed of 6 springs, 7 rivers and one lake, have been installed in order to study the potential contamination by pathogenic bacteria (Listeria, Campylobacter, Yersinia, Salmonella). No salmonella have been found, but several other species have been identified in the water samples of the different study sites: Campylobacter jejuni, C. coli, C. fetus Listeria monocytogenes (sv 1 /2a, 1/2b, 4b), L. ivanovii ivanovii (sv 5) Yersinia intermedia, Y. frederiksenii, Y. enterocolitica, Y. kristensenii, Y. pseudotuberculosis. The most frequently identified species in the studied sites is C. jejuni. It has been isolated in 75% of the sites, with an average percentage of isolation of 11% of' the spring samples, 22% of the river and 56% of the lake samples. L. monocytogenes has been isolated several times in 9 of the 14 sites. It is less abundant than C. jejuni, except in the analysed springs. The presence of C. jejuni and L. monocytogenes 4b has shown to be closely related to the summer pasturing period. Other germs, like L. monocytogenes 112a and yersinias show a uniform annual distribution. The presence of bacteria in surface and groundwater is controlled by several factors, of which the presence of animals, precipitation and temperature have been identified to be the most conclusive ones. In case of source contamination, the factors controlling the presence or absence of pathogen bacteria are different for the case of surface and groundwater: In the first case, the influences of the hydroclimatological conditions are dominant, whereas in the second case it is controlled mainly by the local hydrogeological characteristics. In case of aquifers with interstitial porosity (Clos Ister, Confluent), the presence of pasturing anirnals is however the controlling factor. The persistence of a contamination is controlled by the storage capacity of the catchment basin and by the relation of seep water to the aquifer total volume. In the Brassus spring case, the presence of animals on the catchment area can not explain by itself the bacteriological findings. The presence of the found pathogen bacteria can however be explained by their transport by the run-off rain. The presence of pathogen germs and bacterial pollution indicators has been analysed in a comparative study. Result: 2.3% of the samples contained pathogen germs without containing bacteriological contamination indicator. The species found in the absence of bacterial pollution indicators, are rare species, showing a monotonous annual occurrence. They have been found only in low concentration and the danger when drinking this contaminated water was very small. That means the bacterial pollution indicators choice presently used for water bacteriological quality evaluation is accurate. However, they should be tested with high flow levels, when bacteriological contaminations are particularly important.

EPFL1999