Clouds as a result of transpiration of the Amazon Rainforest

The water cycle, also known as the hydrologic cycle or the H2O cycle, describes the continuous movement of water on, above and below the surface of the Earth.

The mass of water on Earth remains fairly constant over time but the partitioning of the water into the major reservoirs of ice, fresh water, saline water and atmospheric water is variable depending on a wide range of climatic variables. The water moves from one reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by the physical processes of evaporation, condensation, precipitation, infiltration, runoff, and subsurface flow. In so doing, the water goes through different phases: liquid, solid (ice), and gas (vapor).

The water cycle involves the exchange of energy, which leads to temperature changes. For instance, when water evaporates, it takes up energy from its surroundings and cools the environment. When it condenses, it releases energy and warms the environment. These heat exchanges influence climate.

The Sun, which drives the water cycle, heats water in oceans and seas. Water evaporates as water vapor into the air. Evapotranspiration is water transpired from plants and evaporated from the soil. Rising air currents take the vapor up into the atmosphere where cooler temperatures cause it to condense into clouds. Air currents move water vapor around the globe, cloud particles collide, grow, and fall out of the upper atmospheric layers as precipitation. Most water falls back into the oceans or onto land as rain, where the water flows over the ground as surface runoff. A portion of runoff enters rivers in valleys in the landscape, with streamflow moving water towards the oceans. Runoff and water emerging from the ground (groundwater) may be stored as freshwater in lakes. Not all runoff flows into rivers, much of it soaks into the ground as infiltration.

Some water infiltrates deep into the ground and replenishes aquifers, which can store freshwater for long periods of time. Some infiltration stays close to the land surface and can seep back into surface-water bodies (and the ocean) as groundwater discharge. Some groundwater finds openings in the land surface and comes out as freshwater springs. In river valleys and flood-plains there is often continuous water exchange between surface water and ground water in the hyporheic zone. Over time, the water returns to the ocean, to continue the water cycle.

Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as from leaves but also from stems and flowers. Leaf surfaces are dotted with pores called stomata, and in most plants they are more numerous on the undersides of the foliage. The stomata are bordered by guard cells and their stomatal accessory cells (together known as stomatal complex) that open and close the pore. Transpiration occurs through the stomatal apertures, and can be thought of as a necessary "cost" associated with the opening of the stomata to allow the diffusion of carbon dioxide gas from the air for photosynthesis. Transpiration also cools plants, changes osmotic pressure of cells, and enables mass flow of mineral nutrients and water from roots to shoots.

What is Green Infrastructure?Green Infrastructure can be broadly defined as a strategically planned network of high quality natural and semi-natural areas with other environmental features, which is designed and managed to deliver a wide range of ecosystem services and protect biodiversity in both rural and urban settings.

European CommissionBuilding a Green Infrastructure for Europe

Green Infrastructure is a concept originating in the United States in the mid-1990s. Also known as “blue-green infrastructure” or “green-blue urban grids” the terms are used by many design, conservation and planning related disciplines and commonly feature stormwater management, climate adaptation and multifunctional green space.

The United States Environmental Protection Agency (EPA) has extended the concept of “green infrastructure” to apply to the management of stormwater runoff at the local level through the use of natural systems, or engineered systems that mimic natural systems, to treat polluted runoff.

Today, many cities are facing severe water uncertainties, such as floods, droughts and upstream activities on trans-boundary rivers. The increasing pressure, intensity and speed of urbanisation has led to the disappearance of any visible form of water infrastructure in most cities.

One fifth of the world’s population live in areas of water scarcity. Climate change and water-related disasters will place increasing demands on urban systems and will result in increased migration to urban areas. Cities require a very large input of freshwater and in turn have a huge impact on freshwater systems.

http://en.wikipedia.org/wiki/Green_infrastructure

At the scale of a city or county, green infrastructure refers to the patchwork of natural areas that provides habitat, flood protection, cleaner air, and cleaner water.At the scale of a neighborhood or site, green infrastructure refers to stormwater management systems that mimic nature by soaking up and storing water.

StormwaterWhen it rains, some water is absorbed through pervious surfaces—such as vegetated areas with uncompacted soil, sand, or gravel that allow the passage of water. Other water, called stormwater, flows over impervious surfaces—such as rooftops, sidewalks, and streets that obstruct natural infiltration.

Impervious cover exacerbates the problem of stormwater when runoff flows directly into the nearest storm drain without being mitigated. If untreated before entering our waterways, this contaminated water can have a detrimental effect on water quality.

The more impervious surfaces there are in the city, the more polluted stormwater enters the sewer system, increasing the total volume of water the city's infrastructure network must handle.

Below ground lies a vast network of underground pipes. In Philadelphia, we have two types of sewer systems.In areas with combined sewers, a single pipe carries both stormwater from streets, houses, and businesses as well as waste water from houses and businesses to a water treatment plant.

In areas with separate sewers, one pipe carries stormwater to the city's streams while another carries wastewater to a water treatment plant.

When it rains and the volume of combined stormwater and wastewater is larger than the combined sewer system's capacity, the mixed stormwater and wastewater is discharged into the city's streams at a combined sewer outfall (CSO) before it is treated.

n the separate sewer system, stormwater is not routed to a treatment plant and is discharged directly to a stream. Pollutants picked up as the stormwater ran off the city's impervious surfaces are discharged into the streams.

How long is the infrastructure expected to last?

Green stormwater infrastructure includes a range of soil-water-plant systems that intercept stormwater, infiltrate a portion of it into the ground, evaporate a portion of it into the air, and in some cases release a portion of it slowly back into the sewer system.

Our vision is to protect and enhance our watersheds by managing stormwater runoff with innovative green stormwater infrastructure throughout our City, maximizing economic, social, and environmental benefits for Philadelphia.

Green RoofA green roof is a roof or section of roof that is vegetated. A green roof system is composed of multiple layers including waterproofing, a drainage layer, an engineered planting media, and specially selected plants. Green roofs can be installed on many types of roofs, from small slanting roofs to large commercial flat roofs. Two basic types of green roofs have been developed: extensive and intensive. An extensive green roof system is a thin, lighter-weight system planted predominantly with drought-tolerant succulent plants and grasses. An intensive green roof is a deeper, heavier system designed to sustain more complex landscapes. A green roof is effective in reducing the volume and velocity of stormwater runoff from roofs by temporarily storing stormwater, slowing excess stormwater release into the combined sewer system, and promoting evapotranspiration.

Stormwater Tree TrenchA stormwater tree trench is a system of trees that are connected by an underground infiltration structure. On the surface, a stormwater tree trench looks just like a series of street tree pits. However, under the sidewalk, there is an engineered system to manage the incoming runoff. This system is composed of a trench dug along the sidewalk, lined with a permeable geotextile fabric, filled with stone or gravel, and topped off with soil and trees. Stormwater runoff flows through a special inlet (storm drain) leading to the stormwater tree trench. The runoff is stored in the empty spaces between the stones, watering the trees and slowly infiltrating through the bottom. If the capacity of this system is exceeded, stormwater runoff can bypass it entirely and flow into an existing street inlet.

Stormwater Bump-OutA stormwater bump-out is a vegetated curb extension that protrudes into the street either mid-block or at an intersection, creating a new curb some distance from the existing curb. A bump-out is composed of a layer of stone that is topped with soil and plants. An inlet or curb-cut directs runoff into the bump-out structure where it can be stored, infiltrated, and taken up by the plants (evapotranspiration). Excess runoff is permitted to leave the system and flow to an existing inlet. The vegetation of the bump-out will be short enough to allow for open sight lines of traffic. Aside from managing stormwater, bump-outs also help with traffic-calming, and when located at crosswalks, they provide a pedestrian safety benefit by reducing the street crossing distance.

Stormwater planterA stormwater planter is a specialized planter installed in the sidewalk area that is designed to manage street and sidewalk runoff. It is normally rectangular, with four concrete sides providing structure and curbs for the planter. The planter is lined with a permeable fabric, filled with gravel or stone, and topped off with soil, plants, and sometimes trees. The top of the soil in the planter is lower in elevation than the sidewalk, allowing for runoff to flow into the planter through an inlet at street level. These planters manage stormwater by providing storage, infiltration, and evapotranspiration of runoff. Excess runoff is directed into an overflow pipe connected to the existing combined sewer pipe.

Rain Barrel or CisternA rain barrel or cistern is a structure that collects and stores stormwater runoff from rooftops. The collected rain water can be used for irrigation to water lawns, gardens, window boxes or street trees. By temporarily holding the stormwater runoff during a rain event, more capacity can be added to the city’s sewer system. However, rain barrels and cisterns only serve an effective stormwater control function if the stored water is used or emptied between most storms so that there is free storage volume for the next storm. Rain barrels are designed to overflow into the sewer system through the existing downspout connection in large storm events. Although these systems store only a small volume of stormwater, collectively they can be effective at preventing large volumes of runoff from entering the sewer system.

Rain Garden and SwaleA rain garden is a garden designed to collect runoff from impervious surfaces such as roofs, walkways, and parking lots, allowing water to infiltrate the ground. The garden is normally moderately depressed (lower than the surrounding ground level), with the bottom layer filled with stone so runoff can collect and pond within it. The site is graded appropriately to cause stormwater to flow into the rain garden area from the nearby impervious area. The water ponds on the surface, is used by the vegetation in evapotranspiration, and infiltrates into the subsurface stone storage and soil. Rain gardens can be connected to sewer systems through an overflow structure, but usually they are sized to infiltrate the collected stormwater runoff within 72 hours. Flexible and easy to incorporate into landscaped areas, rain gardens are suitable for many types and sizes of development and retrofits. Rain gardens are effective at removing pollutants and reducing stormwater runoff volume.

Flow-through PlanterA flow-through planter is a structure that is designed to allow stormwater from roof gutters to flow through and be used by the plants. Flow-through planters are filled with gravel, soil, vegetation and a connection to the roof downspout to let water flow in. They temporarily store stormwater runoff on top of the soil and filter sediment and pollutants as water infiltrates down through the planter. They are typically waterproofed, and the bottom of the planter is normally impervious. As a result, planters do not infiltrate runoff into the ground; they rely on evapotranspiration and short-term storage to manage stormwater. Excess water can overflow into the existing downspout connection. Flow-through planters can be constructed in many sizes and shapes and with various materials, including concrete, brick, plastic lumber, or wood.

2. flow-through planters1. Infiltration Planters

Pervious PavementPervious pavement is a specially designed pavement system that allows water to infiltrate through the pavement and never become runoff. This system provides the structural support of conventional pavement but is made up of a porous surface and an underground stone reservoir. The stone reservoir provides temporary storage before the water infiltrates the soil. There are many different types of porous surfaces, including pervious asphalt, pervious concrete, and interlocking pavers. Interlocking pavers function slightly differently than pervious concrete and asphalt. Rather than allowing the water to penetrate through the paving, pavers are spaced apart with gravel or grass in between to allow for infiltration.

Green StreetsGreen streets and alleys integrate green infrastructure elements into the street and/or alley design design to store, infiltrate, and evapotranspire stormwater. Permeable pavement, bioswales, planter boxes, and trees are among the many green infrastructure features that may be woven into street or alley design.

La raccolta e il riuso delle acque di pioggia

Le acque meteoriche rappresentano una fonte rinnovabile e locale e richiedono trattamenti semplici ed economici per un utilizzo limitato a certe applicazioni. In generale, gli impieghi che si prestano al riutilizzo delle acque meteoriche riguardano usi esterni, come:- l'irrigazione di aree a verde, prati, giardini, orti;- il lavaggio di aree esterne (strade, piazzali, parcheggi, balconi) e automobili; - usi tecnologici (ad esempio acque di raffreddamento);- alimentazione delle reti antincendio;

e usi interni agli edifici, come:- l'alimentazione delle cassette di risciacquo dei WC;- l'alimentazione di lavatrici;- usi tecnologici relativi, come ad esempio sistemi di climatizzazione passiva/attiva.

Schema di un sistema di raccolta della pioggia

Immagini di G.Conte, IRIDRA s.r.l.

Schema tipo di riuso delle acque grigie

Le tecniche di depurazione naturale

Un sistema di fitodepurazione è un ecosistema umido artificiale, in cui le varie componenti (piante, animali, microrganismi, terreno, radiazioni solari) contribuiscono alla rimozione degli inquinanti presenti nelle acque di scarico. Nei fitodepuratori si riproducono le caratteristiche di un ecosistema naturale, dove la materia viene continuamente riciclata, così la biomassa batterica viene utilizzata da organismi superiori ed entra nella catena alimentare. Le piante utilizzano i nutrienti presenti nel sistema (prodotti della biodegradazione) per il loro accrescimento, rimuovendoli dalle acque. Alla fine del processo tutti gli inquinanti vengono trasformati in anidride carbonica, acqua o “incorporati” nella biomassa.

Nell’ambito delle tecniche di depurazione naturale esistono diverse soluzioni impiantistiche:

FWS: i sistemi a flusso libero riproducono quanto più fedelmente una zona palustre naturale, l’acqua è a diretto contatto con l’atmosfera e generalmente poco profonda, le specie vegetali che vi vengono inserite possono essere di moltissime specie e con diverse caratteristiche (galleggianti, radicate sommerse, radicate emergenti), purché acquatiche. Questa tecnica – certamente la più interessante dal punto di vista paesaggistico – deve essere applicata su acque poco inquinate, ad esempio acque di prima pioggia o acque nere/grigie che hanno già subito un trattamento precedente con sistemi a flusso sommerso.

SFS-h o HF: i sistemi a flusso sommerso orizzontale sono bacini riempiti con materiale inerte (ghiaia) in cui i reflui scorrono in senso orizzontale in condizioni di saturazione continua, le specie vegetali utilizzate sono sempre macrofite radicate emergenti, generalmente la cannuccia di palude (Phragmites australis). E’ il sistema più semplice e più adatto a contesti dove si prevede di fare scarsa manutenzione (ad esempio impianti condominiali per il trattamento delle acque grigie).

SFS-v o VF: i sistemi a flusso sommerso verticale sono vassoi riempiti con materiale inerte in cui i reflui scorrono in senso verticale in condizioni di saturazione alternata (reattori “batch”), le specie vegetali utilizzate sono sempre macrofite radicate ed anche in questo caso generalmente la cannuccia di palude. Sono gli impianti più adatti per acque con valori elevati di carico organico o di ammoniaca. Richiedono però l’utilizzo di pompe o di specifici meccanismi per l’alimentazione.

Impianto di fitodepurazione del Comune di Dicomano, progetto IRIDRA, firenze 2003

Impianto di post trattamento con fitodepurazione del depuratore delComune di Jesi, progetto IRIDRA, Ancona 2000

Impianto di fitodepurazione dell'Hotel Certosa, progetto IRIDRA, Firenze 2002

Impianto di fitodepurazione dell'Ostello dell'Isola Polvese sul lago Trasimeno, progetto IRIDRA, Perugia 2000

La fitodepurazione è una tecnica “estensiva” e richiede quindi una certa disponibilità di spazio per garantire una buona efficacia.

Il dimensionamento di un impianto viene fatto in funzione dei limiti allo scarico (che possono variare anche considerevolmente in funzione del corpo recettore) e delle caratteristiche chimiche delle acque di scarico.

Una stima di massima (cautelativa) dell’area necessaria per il trattamento con la tecnologia più diffusa (SFS-h) prevede circa 4 m2 per abitante per il trattamento di un’acqua mista e circa 2 m2 per abitante per il trattamento delle sole acque grigie. I costi di realizzazione degli impianti sono stimabili in:

FW 40 € m2 SFS-h 100 € m2

SFS-v 120 € m2

Cheonggye Stream in downtown SeoulAn elevated highway had been built through Seoul in 1976 as a way to boost economic prospects in a low-lying area which had become a slum. In 2003, the city's mayor proposed to remove the freeway and and turn the site into green space, which also required naturalizing the creek that once ran there.Not only has the greenway become a well-loved part of the city, it has proven to benefit the city in many different ways. The temperature of the inner city has dropped several degrees, and birds, fish and other wildlife have returned to the urban core. Also, since the freeways were removed, fewer people are driving into the city, choosing to take public transit or other options.

Life beneath the asphaltWhat was built in Seoul, Korea, in the 1960s as the road to efficiency, became a health and safety hazard for the people of the city. The decision to dismantle an elevated highway and a buried polluted sewer was based on the expense of adding reinforcement and ongoing maintenance. What began as a question of cost evolved into a question of value. Cheonggyecheon River has been transformed from traffic corridor into people-friendly destination. Seoul has been reunited with its past history, its present culture and its future market.http://www.dac.dk/en/dac-cities/sustainable-cities/

Flussbad, Realities:United, Bronze Global Holcim Award 2012, Gold European Holcim Award 2011.

The Spree River splits in two in the heart of Berlin and flows around the touristy museum island. After the Berlin Wall came down, there was a huge influx of residents and open space has decreased significantly. This new pool would provide space for leisure and recreation with an even greater bonus of cleaning up the city’s water through natural methods. The beginning portion of the canal would be filled with reed beds and subsurface sand bed filters. After 780 meters of filtration, the water would be sufficiently clean for people to be in it, and the sides of the canal would be converted into stairs to provide access to the water. Incoming drainages would be diverted to the river to maintain the water quality of the pool. Bridges, landings, and decks would offer space to relax and watch the activity. The new pool would be 745 meters long, with specific areas cordoned off for laps, free swim, and even boating. Next to the pool, a new locker and shower facility would be built to support the water activities.