Issue link: https://maltatoday.uberflip.com/i/1473504
15 maltatoday | SUNDAY • 17 JULY 2022 NEWS A typical rainwater harvesting system schematic: a disregarded legal obligation is for all residences to have a cistern. Up until 2012, this was regulated by the Code of Police Laws, where all houses were obliged to have cisterns that could hold at least 3 cubic metres for every 5sq.m of floor area, of each room. In 2015, new rules demanded suitable wells for new or renovated buildings harvesting for rain falling on roofs, which is then channelled to underground, rock-cut cis- terns or tanks, for storage as second-class water. By meeting the demand for second-class water within res- idences, office blocks, gardens, farms, or industrial concerns, the use of groundwater could be avoided, reducing stress on the underground aquifers. "The potential for indirect aq- uifer recharge systems (using urban runoff) to make a sig- nificant positive impact on the recovery and rehabilitation of Malta's groundwater systems is huge"." It could also help in reduc- ing flooding, because modern buildings have changed the way rainwater finds its way into the ground and watercourses. When rain falls on impervious surfaces, much more of it turns into runoff, which can cause flooding, pollution, and land erosion. And GSI technologies could be utilised in urban greening projects. "It would be thought- less to begin to plan for green spaces without provision of ap- propriate, properly engineered and managed water supplies, and it would be tragic if such a supply were to be dependent on abstracted groundwater or mains water, which are cur- rently the main water sources for much of Malta's current landscaping," the report states. Green roofs are also recom- mended as a way of preventing rainwater from being diverted into the streets or the sewer system. Trees in urban areas, apart from beautifying surroundings, also have a fundamental role in filtering out pollutants from runoff water. In fact robust resilient trees can metabolize contaminants (heavy metals, inorganic and organic com- pounds) into their carbon-rich heartwoods, removing them from the runoff. Many trees are also able to remove a wide va- riety of pollutants from soil in- cluding metals, pesticides and organic compounds One suggestion is the de- velopment of 'pervious' – po- rous – pavements which allow rainwater to infiltrate beneath its layers to be stored under- ground or diverted down- stream. Havoc of diverting rain to sewers The report laments that over the last decades, urban runoff has been allowed to be collect- ed and channelled into roads or sanitary sewers. "Convey- ing water away as quickly as possible from a development may adequately protect it from flooding but increases the risk of flooding occurring down- stream." Although disposal of rainwa- ter to sewers has always been illegal, for the past decades rainwater connections have of- ten been made to the sewers, creating periodic overflows out of manhole covers and back- flows in pipes during heavy storms. These overflows result in health hazards, damage to a properties and financial losses due to insurance claims and settlements. Another disregarded legal ob- ligation is for all residences to have a cistern. Up until 2012, this was regulated by the Code of Police Laws, where all hous- es were obliged to have cisterns that could hold at least 3 cubic metres for every 5sq.m of floor area, of each room. In 2015, new rules demanded suita- ble wells for new or renovated buildings. A 2014 study for the Vallet- ta 2018 Foundation had found only 15.2% of residences in Valletta had a cistern. Of these, just one in three houses col- lected the rainwater, which means 95% of the rain falling on residential rooftops in Val- letta ends up in the sewers or as runoff. If nothing is done to address the situation flooding can only get worse, according to the ex- perts drafting the report. Apart from the risks posed by climate change and a greater frequency of storm events, the four-storey blocks replacing townhouses are obliterating gardens and cisterns. "The dra- matic increase in urban devel- opment in the last decades has drastically altered the physical characteristics of the land- scape, increasing the sealing of land and, thereby, reducing infiltration processes." The consequence of this has been a decrease in natural groundwa- ter recharge. There is now an obvious need to effectively manage the con- sequential increase in runoff generation, to reduce flood risks and safeguard – and where possible augment – freshwater sources. Crucially, despite a €51 mil- lion investment in the Nation- al Flood Relief Project (NFRP) – a system of tunnels divert- ing rainwater to the sea – the system cannot cope with mas- sive storms, whose frequency is bound to increase as climate patterns change radically. A case in point is the 2021 storm in November: "As a result, there was flooding across the country, with dozens of vehi- cles submerged, swept away, an elderly man needing airlifting, and various walls collapsing." The flooding was also ex- treme in the areas protected by the NFRP, with the report con- cluding that "it is evident that the NFRP does not cope with events with return period high- er than five years." Crucially, despite a €51 million investment in the National Flood Relief Project (NFRP) – a system of tunnels diverting rainwater to the sea – the system cannot cope with massive storms, whose frequency is bound to increase as climate patterns change radically The dramatic increase in urban development in the last decades has drastically altered the physical characteristics of the landscape, increasing the sealing of land and, thereby, reducing infiltration processes By meeting the demand for second- class water within residences, office blocks, gardens, farms, or industrial concerns, the use of groundwater could be avoided, reducing stress on the underground aquifers 2014 study for the Valletta 2018 Foundation had found only 15.2% of residences in Valletta had a cistern. Of these, just one in three houses collected the rainwater, which means 95% of the rain falling on residential rooftops in Valletta ends up in the sewers or as runoff