Landscape series: 6 Inconveniences in the home neighborhood in Aruba “Typical wildered open cacti-scrub landscape Overgrown by grasses: former agricultural Cunucu” Photo: Ruud Derix, 2003 The Aruban landscape has undergone many changes in history. This paper is part of the landscape series: “Spatial Developments in the Aruban Landscape: A multidisciplinary GIS-based approach derived from geologic, 2016 historic, economic and housing information” Table of contents Inconveniences in the home neighborhood ...................................................................................................................................................... 3 Environment issues that cause inconveniences at home .................................................................................................. 4 Comparison between the data of 2000 and 2010 ............................................................................................................. 4 Prevalency in 2010 across 200x200 meter grid ................................................................................................................. 4 Dust ................................................................................................................................................................................ 5 Noise .............................................................................................................................................................................. 5 Stray Dogs ...................................................................................................................................................................... 7 Soil enrichment, land-based pollution and rainwater runoff into the marine waters .......................................... 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Hidden disruptive processes in the environment .............................................................................................................. 7 The effluence of pollutants from liquid waste ............................................................................................................... 8 A troublesome local situation with limestone terraces along the coast ........................................................................ 8 Monitoring the discharge of nutrients and contaminants ............................................................................................. 9 Incidental flooding ........................................................................................................................................................... 10 Characterization of the flood prone areas ................................................................................................................... 10 Flooding of cesspools and septic water infiltration ..................................................................................................... 12 Changes in the micro-climate conditions ........................................................................................................................................................ 13 Concluding remarks ........................................................................................................................................................................................ 14 Works Cited .................................................................................................................................................................................................... 15 We like to thank our colleagues at the CBS for their general comments on the manuscript. Special thanks to Miriam Helder, Trade Statistics, for the support with relevant data, and, to Marlon Faarup, Director CBS, for the thorough review and remarks on the final manuscript. Author: Ruud R. W. M. Derix, PhD Head department Spatial and Environmental Statistics Central Bureau of Statistics Aruba 2016 II This paper is part of a series on the developments that & Murdoch, 2011). This is what we intend in this study. The relate to the Aruban landscape. To bring into perspective Census in 2010 included questions about how household the current environmental threats and developments, we members valuated the surroundings of their living quarter. review aspects of inconveniences that Aruban household The primary question was: “Do you or more members of members experience within the direct neighborhood of the household, experience any inconvenience in your their living quarter. We call the circumstances that immediate environment from…..example 1, example2, surround these inconveniences conflict situations. Insight in etc.” conflict situations that relate to the local environment is vital to understand the effect of for instance urbanization Figure 1 Administrative regions in Aruba are and other socioeconomic developments on wellbeing and hierarchically organized. The map shows the developments in land-based and marine ecosystems. the subsequent GAC-regions recognizable by the yellow borders that are each subdivided into smaller GAC-zones (recognizable by the different color shading At the basis of tourism in Aruba lies the natural beauty of and numbering). coastal waters and ecosystems. Few people, however, understand that the quality of the coastal land arises not just from geological inheritance, but that it is dependent on present-day processes on land and at sea, and, that the crystal clear waters and fauna-rich marine ecosystems depend on a very delicate environmental balance between land and sea. It is a cynical truth that the success and economic developments on land undermine the quality of these ecosystems, posing a threat to nature and, therefore, also to tourism exploitation itself. Economic developments come with human interference, This habitat destruction, pollution and waste. In the limited simple yes availability of space on a small island like Aruba, or no sustainability is built on the delicate relationship between question provides occurrences on land and at sea, i.e. changes in the us the insight in how landscape and environment are influenced by changes in household members the socio-economy and vice versa. Sustainable experience a number of issues in management requires anticipation and fine-tuning of the vicinity of their home. current general knowledge. What makes “calibrating” Perception-based questions like these actions a challenge is that the effects of human impacts carry some amount of subjectivity as partially remain hidden and accumulate until the threshold inconveniences may be remembered differently level is surpassed at which the effects become apparent. dependent on circumstances and timing. It is a strong For instance, chemical pollution of groundwater and soils argument, however, that something may be out of the poses a risk to the environment and to public health with ordinary when several households in the same possibly long-term and costly consequences, but until it is neighborhood share a similar perception. Similar questions significant the processes of chemical pollution are easily were asked in earlier Censuses, thus we can compare the overlooked. spatial distribution of inconveniences over several decennia. Methodologically, however, a comparison In this paper we will focus on the interface between the between years, is only possible at the level of GAC-zones1, economy, society and the environment, where the results i.e. at less spatial detail (Figure 1) since the GAC-zone is the from human economic action start to bounce back on the highest level of detail that both the Census in 2000 and wellbeing. First, we will focus on the apparent 2010 have in common. Moreover, due to the large surface inconveniences at home in respect to the local extent of some zones it is difficult to link findings to local neighborhood. Home is considered the place in which we spatial characteristics at a finer spatial detail. experience most of our quality of life and where we are meant to experience the security of a shelter. Next, we will investigate some of the more ‘hidden’ processes in the environment that accompany economic development and 1 The Geographical Address Classification system (GAC, 2012) is an that may not yet be in tune with our efforts to attain administrative system of classification that was developed in sustainable living. Aruba for the purpose of information analyses. Its hierarchical structure enables users to present information at three different Inconveniences in the home neighborhood administrative levels. The GAC-system divides Aruba into 8 regions The spatial analysis of inconveniences that are experienced (see figure 1). Each of these regions is divided into a number of in the neighborhood of households can provide insight in zones. Each zone consists of a number of streets or neighborhoods that however cannot easily be displayed as a surface area since the distribution of potential risks to environmental and the addresses do not fall exclusively in a specific area but overlap public health. A higher spatial resolution of the mapping of in space. A few zones (in particular along the Northeast coast) still residential concern pinpoints areas of conflict that remain largely unpopulated. otherwise may remain unnoticed (Leonard, Caughy, Mays, 3 Therefore, in 2010, in preparation of the Census, we The results show that the proportion of households that anticipated that we should be able to perform data indicated to experience inconvenience from dust dropped analysis preferably at a higher spatial resolution. To within all GAC-zones. This does not imply that households overcome the lack of spatial detail we were able to do not experience inconveniences from dust anymore in aggregate and disseminate, in compliance with the rules of 2010, but suggests that there has been a positive change privacy protection, the point-based Census information at towards improvement in how household members the level of GAC-zones, as well as at the level of a range of experience the direct surroundings of their home with grid-tessellations with smaller square areas. regard to nuisance from dust. In regard to noise the situation appears to have improved in 61% of all zones. Environment issues that cause inconveniences at In contrast, with regard to inconvenience from air home pollution, that was exemplified by stench, exhaust fumes, We reviewed if households experience inconveniences or soot in the direct environment of the home, the from ‘dust’, ‘air pollution’, ‘noise’, ‘traffic’, ‘flooding after situation worsened in 69% of all zones. heavy rains’, ‘litter and accompanying stench’, ‘car wrecks’ Similarly, inconvenience from flooding after heavy rainfall and ‘stray dogs’. Some households refrained from worsened in 82% of all zones in 2010 compared to 2000. participation in response to these types of questions (between 0.5% and 0.7%). Dust is caused by the dry climate and constant (Northeast Trade) winds and is a common problem in Aruba, particularly in the more open areas. Households were asked specifically about whether they experienced some inconvenience due to an excess of dust, caused for instance, from excavations, dirt roads or new construction nearby. In similar fashion we asked about air pollution2, exemplified as inconvenience for instance from stench, exhaust fumes, soot, etc., about noise, exemplified as sound hindrance from airplane traffic or neighborhood nuisance, about traffic, exemplified as inconvenience from unsafety or other traffic related activity, and about litter, Figure 2 Relative level of inconveniences in 2010 per type of exemplified as inconveniences from dumped litter or such inconvenience and distribution over the 200x200m residential areas. activities in the direct neighborhood of the living quarter. Prevalency in 2010 across 200x200 meter grid Inconvenience from Dust Noise Air Pollution Flooding We researched the occurrence of inconveniences from dust, flooding, litter, air pollution, noise, car wrecks, and N zones with a decrease in stray dogs in more spatial detail at the level of 200x200 inconveniences 49 30 15 9 square areas to be better able to discern whether the N zones with an increase in inconvenience 0 19 34 40 inconvenience is concentrated in a specific area or whether Total GAC-zones 49 49 49 49 the phenomenon is more common and occurs in all corners of the island. As the visualization by grids is a new % of zones with a decrease 100% 61% 31% 18% and more recent method, only the data from the Census in % of zones with an increase 0% 39% 69% 82% 2010 could be used for this analysis. The local concentration of prevalent grid cell areas, i.e. 200x200m Table 1 Number of GAC-zones where there was an increase area in which more than 50% of households experiences (worsening situation) or decrease (improvement) in the percentage inconvenience, reveals additional emblematic information of households that experienced the specific inconvenience in their on visual inspection of the map representation. household neighboorhood in 2010 in comparison to the situation in 2000. First, we analyze the spread of inconveniences, expressed Comparison between the data of 2000 and 2010 as the proportion of inhabited 200x200m square areas In table 1 we summarize at the level of zones, changes where we observe prevalence (figure 2). between the 2000 and 2010 with regard to inconvenience We noticed that the proportion of households that from dust, noise, air pollution and flooding. A distinction is expressed some level of inconvenience was relatively high. made per GAC-Zone whether there has been an increase or For instance, inconvenience from flooding was expressed a decrease in the proportion of households that expressed by 31.8% of all households and represents almost a quarter their respective inconveniences in 2010 as compared to (24%) of all inhabited 200x200m areas. 2000. Inconvenience from dust and from stray dogs was similarly reported, i.e. in respectively nearly one out of four (24% of 2 The US Environmental Protection Agency distinguished six major inhabited space) and one out of six (16%) 200x200m square areas. Other kinds of inconveniences were much sources of Air Pollutants: Carbon Monoxide (CO), Lead (Pb), less widespread, such as inconvenience from noise, litter, Nitrogen Dioxide (NO ), Ozone (O ), Sulfur Dioxide (SO), and 2 3 2 car wrecks or air pollution (in respectively 9%, 9%, 4% and Particulate Matter (PM or smaller). 10 8% of the inhabited square areas). Yet, prevalence in 4 inconvenience in one out of every ten 200x200 m areas is sure that there has not been some confusion4 between still considerable. dust or air pollution. The data show the presence of inconvenience from air pollution along some of the main Following, the areas where the majority of households roads as well. This may correctly be considered (categorized as 50-75% and 75-100% of all households in attributable to the perception of small particulate matter the area) expressed their inconvenience is spatially from car exhaust, but it may also come from small visualized in the maps in figure 3c-g. We will discuss each particulate matter caused by the vehicles that swirl up dirt of the conflict situations in more detail, next. The or particles from abrasion of the surface of roads and tires. occurrence of inconvenience from flooding after heavy rainfall is discussed in a separate section in this paper. Our study shows (Figure 3d) that nearly a quarter (24%) of all households experience inconvenience from dust in the Dust surroundings of the living quarter. In general, Dust originates from solid particles (particulate matter) inconvenience from dust appears widespread in Aruba and that primarily come from the soil, carried by the wind by is absent only in or near the dense populated centers of human activities such as from construction and land Oranjestad and San Nicolaas. The spatial pattern of clearance, traffic on unpaved residential roads, or, from households that experience inconvenience from dust the use of off-road vehicles on nature trails. Dust may also reveals some small areas and a single larger area of come from sea salt, pollen, spores, and tire particles as particular concern, i.e. in the north in Aruba. well. Small airborne dust particles are inhalable and can be We lack adequate information about what exactly causes carried long distances by the wind. Large particles from the dust (excavation sites, dirt roads, construction sites, fugitive dust easily settle on the ground or rest on the etc.). In particular the northern region has been under vegetation where it cloaks and suffocates the foliage. construction during the recent decade and many Smaller particles (PM or smaller3) usually remain airborne residential roads remained unpaved. It is likely that in this 10 for a while and when inhaled can cause diseases in the region nuisance from the windblown sand and dust may be lower respiratory tract or in the lungs (Brunekreef & caused by the fine-grained gravel of sandy dirt roads and Forsberg, 2005). the combination of Northeastern Trade winds. Dirt and gravel roads are capable of producing large Noise amounts of dust that can affect not only the vegetation Inconvenience from noise occurs near the Reina Beatrix and health, but even the chemistry of adjacent soils Airport (Figure 3e). It goes without saying that the (Brown, 2009). Therefore, it is very relevant to evaluate the departing and arriving planes may cause hinder from noise type of gravel and sand that is used on dirt roads for those who live near the airport. Some concentration of (Kupiainen, Tervahattu, & Räisänen, 2003). Although the areas with prevalence for inconvenience from noise occurs chemical composition of the dust particles play a role, its along the main road network. Worth mentioning is also the small particle size and the ability to be inhaled deeply into intense traffic in these locations, which may be the main the respiratory tract defines the presence of small dust cause of noise inconveniences. Inside residential particles as a serious health risk factor, particularly in neighborhoods inconvenience from noise may arise as circumstances of prolonged exposure. Monitoring the well, for instance when the residential road serves as concentration of PM and smaller particles (PM and shortcut between different localities. A comparison 10 5 PM ) is an important aspect in health programs. The between the maps of inconvenience from noise and 2.5 ambient airborne PM concentration thresholds are inconvenience from traffic (Derix, 2013) indeed shows commonly regulated under national health and safety some concurrence along a few small roads within codes (Pope, 2000) while internationally the UN/EU have residence neighborhoods and suggests the existence of a set more general regulations to safeguard public health road shortcut at these locations. (unece, 2012). Inconvenience from noise does not only include The definition of dust may not be 100% robust to inconvenience from the sound of airplanes or traffic, but misinterpretation (EPA, 2015). Technically, we defined dust may come from other sources of nuisance within the during the Census as fugitive dust that originates from soil. neighborhood as well. Inside residential areas we If dust incorporates small particles from combustion such recognize ‘hotspots’ where households express their as car exhaust with high carbon content, even if it can inconvenience from noise that is unlikely caused by traffic. cause soiling, this is technically referred to as air pollution. In such cases there may be a local different source of hindrance, such as for instance ‘loud’ neighbors or We explained the definitions that we used during the business activity. Census in 2010 by examples, however, we cannot be 100% 4 Generally speaking, small particulate matter is a type of air pollution but commonly and also so during the Census in 2010 one specific type of small particulates, fugitive dust is considered as a 3 PM10 is particulate matter with an average diameter size of 10 separate category; in our case to be able to label inconveniences microns. This type of particulate matter is considered likely to be from dust from traffic on unpaved roads. The EPA defined Fugitive able to be inhaled and reach into the respiratory tract. PM and emission as particulate matter that is generated or emitted from 5 PM are considered likely to be able to be inhaled and reach into open air operations in contrast to emissions that passes through a 2.5 the respiratory tract as well as deeper in the lungs. stack or a vent) 5 3b 3a 3c 3d 3f 3e 3g Figures 3 c-g show map representations of the spatial distribution of 200x200m square areas that show an above average level of inconveniences in the household for a number of activities in the direct surroundings of the living quarter. The respective square area is highlighted in orange or red color when respectively 50% to 75% percent and over 75 % of the households in that area reported to experience a specific inconvenience. The maps also depict the main road network, as well as economic space (colored in greenish blue) and space reserved for nature (colored in green) (DIP, 2009). The map on top (3b) presents information about the names of local neighborhoods. The small map on the top right (3a) shows the density distribu6tio n of housing units in Aruba as a grid tesselation of 200x200m square areas with each cell catagorically representing the total number of housing units in that specific square area. Air pollution and Litter Soil enrichment, land-based pollution and ‘Simeon Antonio’, ‘Bucuti’, ‘Cas Paloma’ ‘Parkietenbos’, rainwater runoff into the marine waters and to some degree also ‘Mahuma’ are adjoining localities that are situated just south of the Reina Beatrix Airport, Hidden disruptive processes in the environment near the public dumpsite and near businesses that use Little is known by the public about the Caribbean Sea heavy road equipment. These neighborhoods are of which is under continuous stress from eutrophication and particular concern as a majority of households express pollution. On the scale of regional polluters the position of their inconvenience from noise (Figure 3e) and more so air Aruba has changed drastically in recent years, but the small pollution (Figure 3f) and litter (Figure 3c). island setting allows very little margin for error. A large open waste dumpsite situated at Parkietenbos is After the closure of the oil refinery in 2012, the direct likely to be one of the causes of the inconveniences environmental impact from pollution from the refinery experienced by neighboring households. More recently, a waste separation plant5 was constructed at ‘Parkietenbos’, activities ceased, but the consequences of earlier pollutive actions are still present7. Locally, in San Nicolas, and in the but the open public dumpsite is still operational. near region, problems still reside in the soils (Ridderstaat, Air pollution is an issue in households situated south of the 2007). airport but also near the oil refinery in San Nicolas (Figure Today, pollution confines to small-scale industrial activities 3f). such as from the processing of salt water at the local water Abandoned excavation sites may serve as legal (RWZI- desalinization plant, from the leakage of the open dump dumpsite in Wayaca) or illegal dumpsites (dumpsite at Sero site south of the Airport, from the traditional household Lopez). Both are frequently used as a source for litter, cesspits, in particular in the coastal regions (that leak waste and other types of local disturbance in the wastewater into the groundwater), and from the seasonal surrounding areas. Similar in size as the excavation site in rainwater runoff into the sea. Many local cesspools near ‘Mahuma’ (currently closed) is a site at Alto Vista, in the the coast situate on permeable Limestone Terraces and are northeast, and in the area of ‘Weg Fontein’, north of San traditionally made from bricks and not sealed at the Nicolaas. In both areas we observe heightened levels of bottom. inconvenience by households from litter and stench. Hydrogeological/chemical studies (Finkel & Finkel, 1975) (Borst & de Haas, 2005) have emphasized the importance Stray Dogs of freshwater retention sites to limit erosion and improve The main map in figure 3 shows the locations where hinder the formation of soils for agriculture and vegetation. Long- exists caused by stray dogs. Examples are found all over term monitoring studies of pollution and nutrient- the island, but more so in the more rural regions and less enrichment in the neighboring islands Bonaire and in the city centers of Oranjestad and San Nicolas. In the region of ‘Westpunt’, east of the saliñas6 in the north, and Curaçao stress the impacts of daily pollution and eutrophication on the near shore coastal ecosystems and in ‘Sabana Basora’ and in a number of small locations, we the lack of adequate sewage treatment plants that may observe a concentration of inconvenience from stray dogs. prevent the sewage water to reach the sea (Lapointe & In 1989 (Sprang & Quant, 1989) an inventory survey of Mallin, 2011) (Goreau & Thacker, 1994). A proper water dogs and cats was conducted in Aruba. The study was management on land is relevant for the maintenance of a repeated in 2003 (Rossen, 2003). In 1989, the researchers healthy living environment on land as well as at sea. found that one in three dogs had regular access to roam free outside the compounds, compared to about one in Studies show that marine and terrestrial ecosystems in the four dogs in 2003. In 2003, one in every twenty dogs had Caribbean have difficulty with high levels of nutrient full access to the street at any time of day. Almost two enrichment and thrive best in a nutrient-poor balance of thirds of households owned more than one dog. The state (Siung-Chang, 1997). In the worst case scenario, a relatively high density of residential dogs is in line with the nutrient rich coastal water stimulates microalgae growth level of hindrance in 2010 that is spatially represented in (Lapointe e. a., 1998) and may create oxygen deprived figure 3g. zones. Under such circumstances, water becomes turbid In 2015 new legislation was implemented to assure that (Goreau & Thacker, 1994) and coral communities, households keep their dogs inside their own premises. The mangroves, and sea grass beds will suffer severe damage effort was to prevent hinder from free roaming residential (UNEP, 2015). Other markers of a disrupted marine dogs that disturb/attack pedestrians and cyclists. ecosystem are the lessened presence of predator fish that Stray dogs are still a common sight, however. Mostly, may trigger a population explosion of, for instance, these are abandoned dogs. jellyfish. It is without saying that even a small change in this direction may have a negative impact on the tourism industry. The unforgiving disruptive enrichment by nitrogen and 5 persistent/bioaccumulative substances of the nutrient- Waste to Energy Plant poor (oligotrophic) highly sensitive local marine 6 The saliñas are the coastal wetland areas that still exist in the ecosystems happens in an encroaching slow but Northwest, but that have been blocked from the sea by tidal devastating rate (Greenpeace.org, 2015), (Worldwatch, barriers and road infrastructures. At current, the brackish 2000) (Goreau & Thacker, 1994). floodplain areas still show the characteristics from vegetation’s adaptation to salinity and the presence of typical (migratory) bird species. 7 http://www.oceanhealthindex.org/Countries/Aruba/ 7 The contamination and enrichment of soils from household The effluent of land-based sources on the coastal marine liquid waste and sewage may by itself be mild at any given environment has not been studied thoroughly in Aruba. moment but constituents accumulate in the soil and Effluence can occur via: groundwater on a continual basis (Sharpley A.N., 1996).  Groundwater For instance, an alteration of the soil chemistry and  Rainwater runoff9 acidification of the topsoil8 is described from the local  Direct discharge along the coast disposal of household waste, such as paints, detergents,  Landfill leakage oils and leaking batteries (Pimentel, 2005).  Fall-out at sea as pollutants are carried by the wind What happens next is that when soil constituents lose their binding capacity, nutrients such as nitrates, phosphates Better insight in these processes is relevant and significant and urea find their way more easily from the groundwater to be able to manage the quality of near-coastal waters into marine waters. Similarly, bio-persistent contaminants (Goreau & Thacker, 1994). We give an example of the such as pesticides, heavy metals and household chemicals dimension of pollution that can occur via waste water. accumulate and seep into the deeper soil layers and groundwater and cause harm in the food chain at a large The effluence of pollutants from liquid waste distance from their actual disposal site. The constant drain of nutrients (and bio-persistent toxic substances) from residential living and economic activities Next, we reveal some insight in the ‘hidden’ underlying filtrates in part into the soils and feeds into the process of infiltration of contaminants and nutrients into groundwater. These land-based constituents eventually the natural surroundings and describe the role of typical disperse into the coastal marine waters and overload the geological and societal local circumstances. nutrient-poor (oligotrophic) marine ecosystems. It is obvious that the high population density and impact The disposal of “eye-catching” municipal solid waste is from new building and road construction puts the small recently well-organized, but the disposal of liquid waste scale natural island setting under increasing stress. New still needs more attention. We have to gain information insights learn that the question of when and where to act and grow awareness that helps to overcome and remove has long passed. Several studies in the Caribbean (Lapointe the solved substances of pollution and nutrient- & Mallin, 2011) (Peters, 1997) have documented the effect enrichment before these can cause harm at sea. from land-based runoff, the leaking of landfills, and, the In short, at the regional level, the processes that are less warm water effluence on coral reef growth, or, the harm it eye-catching but create accruing stress to the local marine brings to mangrove ecosystems along littoral coasts. environment are: Comparative studies in Aruba are lacking, however, but  Acidification of marine waters, for instance due to similar situations do exist. rising atmospheric concentrations of carbon dioxide (CO2) and the consequential absorption of the gas A troublesome local situation with limestone terraces along by the oceans. the coast  Sea water temperature rise The total balance of nutrients and contaminants  Contamination and nutrient-enrichment of (fertilizers, oils, salts, pesticides and detergents) that groundwater, in particular on the limestone, and reaches the coastal waters will show considerable seasonal their effluence into the marine waters variation due to the seasonality of heavy rains and rate of evaporation. Acidification may come from (polluted) stormwater runoff As noted before, the geology of the coastal zone in Aruba from land-based (industrial) activities. Unfortunately, we may play an important role in the dynamics of exchange lack information about seawater acidification from land- between land and sea. Most of the inhabited land along based activities. Its impact even at a regional scale, the coast is from karstic and highly permeable limestone however, may remain low since there is little industrial rock (Derix, 2016c). Rainwater from the land interior activity in Aruba. Thermal pollution at sea may come from reaches the porous limestone terraces from where most of ‘coolant water’. Sea water temperature rise is expected to it seeps into the sea, subterranean, via the ground water, have a detrimental effect on marine life, although the via the faults and fracture lines or more directly at the phenomenon is at present insufficiently understood surface via the dry-river systems. During most of the year, (Sewlal, 2010). however, evaporation is so high as to prevent the effluence from leaking cesspools on the Batholith to reach the coastal waters. This may even be the case for many cesspools that are situated on the limestone terraces. In opposite direction, when evaporation is very high during the dry-season, coastal groundwater saline levels may even increase due to infiltration from sea water (Finkel & 8 Nitrogen from wastewater sewage (detergents and urea) is Finkel, 1975). thought to influence the biochemical processes in the soil. While In contrast to the presence of limestone geological there is an acidifying effect (biochemical release of free hydrogen substrate, the compaction of soils and the cementation of (H+) acidic ions against less hydroxyl (OH-) basic ions) from the urban landscape will prevent rainwater to soak into the ammonium nitrogen (urea) in soils, the highly soluble nitrates percolate into the groundwater. Acid surface soil can also increase 9 dissolution of limestone layers and can cause dangerous sinkholes For a general discussion of urban wastewater runoff we refer to in Limestone layers on land. www.environment.nsw.gov.au/stormwater/ 8 soil and therewith increase the amount of urban pollution An alternative objective, therefore, might be to combine that is washed out with surface water. information already gathered from elsewhere and distillate the ‘probably’ that similar situations may occur locally as So, the magnitude of the nutrients and contaminants that well. For instance, a study in 2011 (Lapointe & Mallin, reach the sea may be constrained in time and place but 2011) in Curacao and in Bonaire shows that in relation to also altered dependent on local circumstances. maintaining a healthy deep and shallow reef ecosystem a number of contamination indicators have already Studies conducted in limestone areas in Italy show that in exceeded threshold values. No such studies exist in Aruba, fact limestone is quite effective in the neutralization of but given the relatively similar pressures from population wastewater nutrients, often already within a single km and housing, and a well-comparable climate and geological distance from the infiltration point (Masciopinto & Carrieri, condition, one may carefully consider whether in Aruba, 2002). Unfortunately in Aruba, the limestone rocks are similar contamination of marine waters may occur. only up to 2.5 km wide and situated directly at the coast. Furthermore, the monitoring of net imports and net The chance that polluted groundwater will leak from the exports already provide insight in the level of local usage of limestone into the marine environment is still likely. for instance fertilizers, pesticides, or, cleaning products, Groundwater studies in Aruba (Finkel & Finkel, 1975) have and, therewith, the detrimental impact from disposed focused on the potential reserves of drinking water for chemicals and nutrients via water, land or air. Knowledge agriculture purposes. A baseline study exists, however, about the chemo-physical characteristics and interactions that focuses on anthropogenic influences on groundwater of contaminants with local soil constituents, in quality (Sambeek, Eggenkamp, & Vissers, 2000). The study combination with local hydrological and geomorphological reveals elevated concentration of nitrates in a number of conditions, may be useful to model impacts. wells on the island and suggests that this may relate to the presence of nearby cesspools. In particular, in areas where To get an impression of the amount of chemicals that is there is easy penetrable limestone, aquifers and wells will disposed in the local environment, yearly, we show the be more susceptible to infiltration by persistent organic total yearly import of soaps, detergents, cleansers and compounds and bacteria or viruses from nearby cesspools fertilizers (the respective export figures are generally low and contaminated soils, than in other parts (Wolf, Nick, & and have not been shown in the representation in figure Cronin, 2015). 4). Their findings stress that cesspools need to be able to withstand a period of flooding, in particular in the flood- prone areas, but more preferable, avoid any risk on leaking into the ground water from modern septic systems. Currently, in Aruba, there is a policy to allow only completely enclosed septic tanks for new construction, but the rule is not yet fully legally embedded. Monitoring the discharge of nutrients and contaminants To keep track of the amount of contamination and enrichment from liquid waste10 that reaches the marine environment via ground- and wastewater runoff is a challenging task. In Aruba, coastal water samples are collected and analyzed with the purpose of regularly monitoring the quality standards of safe swim water. Figure 4 presents the weight import figures of respectively soaps, Studies from abroad show that the contamination and detergents and cleansers and of fertilizers, categorized by Aruba nutrients thresholds for safe swim water are actually Customs Authority according to the Harmonized coding System11 insufficient to safeguard the quality of coral ecosystems under category code 06.34 and 06.31, respectively. (Goreau & Thacker, 1994). Besides, while the measurements occur along the shallow coastline, In Aruba, in the absence of e central sewer system in most discharge into the sea may occur via groundwater springs areas, soaps, fertilizers and pesticides are likely to end up that seep off the coast into deeper waters. in the garden soils and cesspools. The utilized substances will disintegrate and interact with soil constituents to In the ideal scenario, we would like to monitor the spatial become harmless substances, but part will accumulate in pattern and intensity of subterranean groundwater in the cycle of contaminated soil, ground- and effluent effluence in combination with the concentrations and waters. On occasion, when disposed with the public waste geochemical interactions between local soil constituents stream the chemicals may be incinerated at the new local and contaminants in Aruba. Such studies, when feasible at waste incineration plant, but we do not expect this to be all, are very costly and may, therefore, never be performed. 11 CBS uses the International General Trade System for the processing and publication of all import and export data by commodities and by country. Total Imports and total export include all goods entering and respectively leaving the economic 10 We define household liquid waste as wastewater with territory of Aruba. The economic territory of Aruba comprises of contaminants of oils or fats, paints, detergents, cooking oils or Aruba (the free circulation area) and the Free Zone Aruba. This is hazardous household liquids, etc. consistent with the General Trade System. 9 the case for most of the cleaners, pesticides and fertilizers. Characterization of the flood prone areas There is no separate waste collection stream for liquid We mentioned already, that a relatively high percentage of waste products (except for some oils, fats and oil residues households (32% in 2010) express experiencing by restaurants and local car repairs, etc.). inconvenience from flooding after heavy rains (figure 2). These households expressed inconvenience from flooding Figure 4 shows a substantial rise (40%) in the import of in nearly a quarter (24%) of all residential 200x200m areas. cleaning products over the last five years (from 2.5 mio. kg In 82% of the GAC zones, the inconvenience from flooding up to 3.5 mio. kg per year). As most of these products will after heavy rains was expressed to be higher in 2010 than end into the soil we assume that there is a steady in 2000 (Table 1). This is an indication that the situation in accumulation of phosphates and nitrogen in the soils that the neighborhoods had worsened over the last decennium. will eventually overload the binding capacity of soil The reason seems straightforward as the density of constituents and wash away. Also, figure 4 reveals a rise in construction there increased over the years. the import of fertilizers, be it in smaller quantities, up to 1 mio kg in 2014. We lack detailed local information about However, many of the flood prone areas are located on the the effect of nutrients and (chemical) constituents on the Lower and Middle Terraces (Busonjé, 1974) along the oligotrophic local marine environment. coast. We typically would not expect flooding areas on a high permeable limestone substrate. The limestone is on Uncontrolled effluence of nutrients and contaminants into average between 15 and 45 meters thick and rests on the sea is influenced as well by local flooding after heavy crystalline rock or on a bed of layered clays and sand. rainfall and run-off into the sea. Furthermore, that close to the sea, the groundwater is only a few decimeters deep and not only the natural water Next, we will provide information about the level of runoff is slow in these low-lying areas, also the incidental flooding after heavy rainfall, based on transmission speed12 in the limestone is too slow to allow a information gathered during the Census in 2010. rapid drain of rainwater. At a groundwater gradient of approximately 0.001 near the coast the transmissibility is Incidental flooding calculated at about 1.1 mm/sec and 2.0 mm/sec at some Local flooding carries a cost of damage to private and distance more near the border with the crystalline public property and infrastructure, causes accidents and Batholith (Finkel & Finkel, 1975). Transmissibility is known inconveniences, and also poses a risk to public health. to become worse with soil compaction and subsurface Mostly, rain falls without causing extreme harm, but every obstruction as occurs, for instance from infrastructures and few years, incidents occur when areas are flooded after from the construction of hotels such as along the coast. heavy rainfall. To catch the incidental rainfall, rainwater dams (locally called ‘Tanki’) are built with the ability to An exceptional high density of households that expressed overflow, but on one such occasion, unexpected damage inconvenience from flooding is located in the Northwest, to private property downstream occurred, when the rising south of Bubali Plas and in San Miguel (Figure 5C) and also mounts of water caused a breach in the Tanki outer wall. in the Southwest, in Pos Chiquito and in Zeewijk (Figure 5D). Three other areas are worth mentioning, i.e. east of In some areas, neighborhoods regularly suffer from the ‘Kamerlingh Onne Straat’ up to the ‘De La Salle Straat’ (in temporary inundation after heavy rains and inhabitants Oranjestad), in the area of Tanki Flip and in the area of feel frustrated by the recurring events. New construction Bucurui/Sabana Liber. Needless to say, there are other constantly changes the face of the landscape and changes smaller spots where residents experience hindrance from the natural course of the rainwater. Sometimes small or flooding after heavy rains. even large dry-river waterways appear to be blocked completely. Later, when extreme rainfall occurs, the new homeowners in these neighborhoods get confronted with problems they were previously unaware of. We analyzed the percentage of households that experience inconvenience from flooding after heavy rainfall in each of a 200x200 meter area. In figure 5 we show the 200x200m square areas where over 50% of households experience inconvenience from flooding after heavy rains and refer to these as the flood prone areas. The data are from the Census in 2010. The maps also show the location of dry-rivers and the location of different watershed areas (figure 5A), the height topology (figure 5B) and the extent of the limestone layer near the coast. The location of the household draining systems is exemplified in more detail in figure 5C and 5D (CBS, 2010). Coincidentally, the Census activities in 2010 took place during a period of intense rainfall. 12 Transmission is the passage of water through the substrate 10