WATER RESOURCES MANAGEMENT A CASE STUDY IN POLLUTION IN A MAJOR RIVER CATCHMENT, TRINIDAD

Floyd Lucas, Zoology Unit, Department of Life Sciences,

The University of the West Indies. Dr. Mary Alkins-Koo, Zoology Unit, Department of Life Sciences,

The University of the West Indies. Introduction Watersheds can provide a number of services to the ecological and human communities that exist within the catchment. Services to human communities include the provision of freshwater, energy, timber resources and flood control. Watersheds can be impacted by the change of land use from forest or natural communities to other land use patterns such as agriculture, residential property and industrial development. Degraded catchments are often the result of Man's activities as land use is changed to suit our needs. Catchment functions and processes become impaired resulting in a decrease in water quality and services provided. The effects of human influences can be difficult to quantify where perturbation and pollutants are derived from numerous sources including non-point sources (Van Hassel et al, 1988). Extremes of degraded conditions are easy to ascertain but moderately degraded sites can be difficult to identify (Fore and Karr, 1996). Changes in land use, from forest to agriculture or urban development, invariably lead to increases in nutrients and suspended solids Changes in land use are complicated through natural ambient conditions such as pH and nutrients in lower catchments determined by soil conditions (Billet and Cresser, 1992; Stevens et al,. 1993; Reynolds et al, 1994). In studies, it is essential not only to compare sites in rivers, but to compare similar catchments. However, the changes in land use do not always lend themselves to comparison by catchment, due to differences in the physical and chemical nature of the catchments. Land use patterns must often be looked at in isolation of other uses due to difficulties when dealing with situations involving multiple perturbations in a catchment (Van Hassel et al, 1988). One type of land use that can have adverse effects on stream quality is agriculture. Agricultural activities can lead to adverse effects on stream communities through high bacterial and viral concentrations, soil erosion and high turbidity, eutrophication resulting from nutrient runoff, increased oxygen demand, pesticides, field underdrainage and the channellisation of watercourses (Dance and Hynes, 1980). Inorganic nutrient input into freshwater ecosystems is another problem that can affect water quality. The lower catchments of streams tend to have higher levels of nitrates which may be as a result of the breakdown of organic material, the atmosphere, nitrogen fixing bacteria and soil. Mature forest may contribute higher levels of nitrates than grasslands. In tropical forests nitrogen may be more tightly cycled due to the fast breakdown of organic material, however,

early flushing during the start of a rainy season may release significant amounts of nitrogen. General household waste in ‘grey water’ may contribute significant quantities of nutrients including nitrates and phosphates. Other uses that may impact on water quality include the use of pesticides for agriculture (Hatakeyama et al, 1990, Cuffney et al, 1984), heavy metals (from point sources or non-point sources),‘and effluent from Sewage Treatment Plants (STPs). Ascertaining the effects of particular pollutants or effluents is difficult when there is a myriad of other sources of pollution and background pollution (Bervoets et al, 1996, Van Hassel et al 1988). In seasonal streams the problem of pollution effects may be even more complex as the contributions of effluent as volume will change between seasons and have varying effects. The Caroni River Basin is one of the largest river systems on the island of Trinidad. The drainage extends from the south-draining slopes of the Northern Range, a mountain system that runs parallel to the north coast of the island and north-facing slopes of the Central Range running along the center of the island (in a southeast to southwest trend). The Caroni River Basin has been a traditional source of water to the people of the island since the time of human colonisation. The largest water treatment facility on the island, the Caroni Arena Water supply system (commissioned in 1981) is situated in the river basin from which water is drawn from the Caroni River. The Caroni Arena Water supply system has the capacity of approximately 273 ml/d (Delft Hydraulics (1999) equivalent to approximately 34% of the total Water and Sewerage Authority (WASA) production. One of the factors that led to the establishment of the facility was the significant dry season flow within the Caroni River. The source is an impounding reservoir at the Arena River, one of the tributaries of the Caroni River. The impounding reservoir is located at San Raphael approximately six kilometres from the Caroni River. Water is released from the reservoir in the dry season to maintain base flow in the Caroni River. The Caroni Arena Treatment facility includes: the reservoir on the Arena River to store run-off from the Arena watershed and provide off-stream storage capacity for water from the Tumpuna River, an intake and pumping station on the Tumpuna River at San Raphael to pump water to the Arena Reservoir, an intake, low-lift pumping station, water treatment plant and high lift pumping station at Kelly village (Piarco), and transmission mains from the high lift pumping station to the northwest and southern areas of the country (DHV Consultants et al 1999). In addition to this system there are major river intakes on tributaries of the Caroni River. All the river intakes in Trinidad are located in the Northern Range. However, there is a seasonal variation in the production from these river intakes with production decreasing during the dry season. The Guanapo Waterworks river intake, the Aripo river intake and the Caura intake have capacities of approximately 11.3 ml/d, 10.0 ml/d and 11.3 ml/d respectively. In addition to these surface water intakes there are producing boreholes for ground water in the Caroni River Basin. A typical groundwater supply system consists of two or more wells from which water is pumped to a central treatment plant. There are three groundwater systems which are considered major in their physical extent and capacity that occur in the Caroni River Basin these are El Soccoro, Valsayn, and Tacarigua.

The Valsayn system consists of 12 production boreholes, the El Socorro system nine production boreholes, and the Tacarigua system ten production boreholes. The El Socorro system has an average production of this system is 23.5 ml/d. Water from the Valsayn boreholes delivers treated water to the Eastern Main Road communities as far as Success Village in Laventille to the west and Tunapuna to the east. The average production of this system is 32 ml/d. The Tacarigua system is used mainly to supply water to the industrial area along the Churchill Roosevelt Highway, the University of the West Indies and to the residential area of Curepe. The average production of the Tacarigua wells is approximately 15 ml/d (DHV Consultants et al 1999). Historically, the foothills of the Northern Range and the Caroni Flood plain was dominated by sugar estates while the upper valleys of the Northern Range and Central Range (where suitable land existed) were used for the production of cacao, and the upper steep slopes in forest. With the depression of the cocoa market in the 1920s the estates were largely abandoned. The pressure on the sugar market and the conflict with land use also resulted in a loss of arable land to the now developed areas along the Eastern Main Road (EMR). Thus the ‘East-West’ corridor developed, an area of dense housing and various other human activities on former estate land. Study Area and Methods Within the Caroni River Basin there is a high degree of heterogeneity in the structure of tributaries. This is evident when the streams that originate in the Northern Range are compared to the streams from the Central Range. This often makes comparison between these areas difficult. For the present study, seven streams of the Northern Range were isolated from the other areas and water quality investigated in order to look at the land use trends and its impact on water quality. This is in an effort to ascertain the land use impacts that are occurring in the Caroni River Basin that may impact on the system and continued dependence for potable water supply. These rivers are: San Juan, St. Joseph, Tacarigua, Arouca, Arima, Guanapo and Aripo (Figure 1). These rivers were selected based on relatively uniform physical features (including size of the catchment) and biological features (in the form of natural vegetation, prior to land use changes). Three of these tributaries have water intakes and treatment facilities. The Arima, Guanapo and Aripo Rivers are upstream of the raw water intake for the Caroni Arena Treatment facility. These rivers are all part of the recharge area for the Northern Gravels from which water is abstracted.

Figure 1: Northern Range Streams

Thus, the major difference between individual rivers is land use patterns (in terms of major type and quantity). General patterns within the individual catchments were investigated from aerial photos, topographical maps and field investigations. This was conducted to deduce overall land use trends. At the time of the survey the Guanapo River had the least impacts in terms of land use change and it can be considered as a control in the study. The fieldwork for the study was conducted between January and December 1999. Two sampling sites were located on each river, an upper site (situated in the mid-catchment) and lower site (close to where the tributary joins the Caroni River). Physico-chemical parameters were monitored on a monthly basis and included Total Nitrates, Total Phosphates, Temperature, Dissolved Oxygen (DO), pH, Total Suspended Solids (TSS), Total Dissolved Solids, and Conductivity. Sampling during the course of the study included field measurements and collection of water samples for laboratory analysis. For the field measurements of pH, conductivity and TDS a Ciba-Corning meter was used. For the laboratory analysis water samples were collected in acid-washed 1-Litre polyethylene bottles. The sample bottle was washed twice with stream water prior to the collection of the water sample at mid-stream.

Laboratory Methods Samples were stored at 4?C and warmed to room temperature before analysis. The water samples were analysed within 24 hours of collection. Nitrate-Nitrogen, Total Phosphorus and Total Suspended Solids were determined using a Hach DR/2000 spectrophotometer. All glassware used in chemical analyses was washed with detergent, acid washed and rinsed with deionised water to prevent contamination of the samples and inaccurate results. The laboratory analyses were conducted to Standard Laboratory Analyses (ref**). Statistical Analysis In order to ascertain trends in the data, Cluster Analysis was used to judge the relationship between rivers and perhaps more clearly link present trends. It was expected that rivers could be placed in into natural groupings based on water quality. The data was analysed using the software, SYSTAT version 9.0 and a Cluster Tree derived. Results General Land Use Field investigations of these rivers show that the Guanapo River, Aripo River, Arima, and Tacarigua River had significant areas of forest cover in the upper catchment. The Guanapo upper watershed was almost entirely forested consisting of mature secondary forest on former cocoa land and primary forest in the upper areas. The Aripo, Arima and Tacarigua Rivers all have primary and secondary forest in the upper watershed. The St Joseph River and the San Juan River had the greatest level of built environment with urban and suburban housing high in the catchment. The Arouca River and the Tacarigua River both had significant agricultural activity in the mid to upper watershed in the form of short-term crops while the Aripo River catchment has poultry and livestock production in the mid catchment. The lower watershed sites all occurred between the Eastern Main Road (EMR) and Churchill Roosevelt Highway that corresponds to the area of densest built environment in the Caroni Basin. This area known as the East-West Corridor has mostly contiguous areas of housing with interspersed light industrial areas. All lower sites were accessed from these major roads Water Chemistry Upper sites showed varying levels of perturbation and potential pollutants (Table 1). Guanapo River showed conditions indicating high water quality as is expected of a near pristine stream with forest cover dominating the upper watershed. Nutrient levels were low and DO was high. Seasonal differences in water quality were not great.

Table 1: Average (? SD) Physico-chemical Conditions in Upper sites

San Juan St Joseph Tacarigua Arouca Arima Guanapo Aripo

Temperature (?C) 24.6?1.6 24.5?1.4 23.1?1.5 23.3?0.9 23.9?2.0 22.2?1.1 23.7?1.7 Total Nitrate (mg/L) 2.13?1.43 1.06?0.50 1.00?0.18 1.14?0.85 0.94?0.28 1.08?0.34 1.48?0.48 Total Phosphate (mg/L) 0.32?0.11 0.58?1.74 0.18?0.12 0.15?0.08 0.16?0.05 0.11?0.06 0.13?0.12 pH 7.8?0.4 7.7?0.3 8.1?0.2 7.8?0.5 8.0?0.4 8.1?0.4 8.0?0.4 DO (mg/L) 7.8?0.7 8.0?0.5 8.4?0.4 8.1?0.5 8.2?0.5 8.5?0.4 8.7?0.5 TSS (mg/L) 5.7?5.0 15.3?12.0 31.0?39.0 4.5?3.6 5.5?4.0 7.3?6.9 4.3?2.9 TDS (mg/L) 295.2?60.3 230.9?77.6 181.9?46.5 126.3?46.7 173.0?67.6 222.9?206.2 207.9?56.9 Conductivity (?S) 585.6?138.6 478.3?155.2 366.7?88.0 269.8?110.5 325.8?128.0 398.4?358.5 384.2?101.2

Table 2: Average (? SD) Physico-chemical Conditions in Lower sites San Juan St Joseph Tacarigua Arouca Arima Guanapo Aripo Temperature (?C) 26.1?2.2 26.6?2.1 25.4?2.1 24.4?1.7 23.9?2.0 25.0?2.3 24.5?1.9 Total Nitrate (mg/L) 1.50?0.77 1.21?0.82 1.14?1.39 1.13?0.32 1.15?0.31 1.02?0.70 1.34?0.45 Total Phosphate (mg/L) 0.40?0.12 2.31?0.57 1.27?0.72 0.44?0.29 0.40?0.16 0.24?0.33 0.61?0.33 pH 7.95?0.54 7.67?0.49 7.56?0.40 7.57?0.63 7.56?0.32 7.67?0.34 7.74?0.38 DO (mg/L) 8.08?1.80 5.82?1.62 4.02?1.85 6.97?0.91 6.89?0.49 8.37?0.75 7.33?0.42 TSS (mg/L) 6.55?4.82 31.00?39.01 24.45?18.26 6.95?6.32 14.59?12.51 10.05?9.85 19.36?8.86 TDS (mg/L) 299.77?58.35 252.41?78.64 206.36?57.57 137.77?38.05 164.05?53.11 143.65?44.58 179.18?48.19 Conductivity (?S) 581.23?119.04 481.41?154.24 392.50?111.38 261.03?90.03 320.95?96.28 276.18?85.44 361.32?70.86

Generally, upper sites showed conditions indicative of mildly polluted systems and cannot be considered severely impacted. However, the San Juan and St. Joseph showed slightly elevated levels of nutrients. Both these systems are characterised by significant residential development and urbanisation in the catchment. The Aripo River upper site showed slightly higher levels of Total Nitrates in the dry season. Lower sites (Table 2) were all situated south of the major residential and commercial areas of the river system. The location of these sites means they are subject to significant inputs of surface run-off, grey water, and sewage. Generally, lower sites are characterised by lower water quality. Among the lower sites the Tacarigua and St. Joseph Rivers were grossly polluted. For most of the dry season and parts of the wet season these rivers had a surficial anoxic layer. The Arima River site, downstream of the town of Arima, had better water quality, possibly a result of a higher percentage of forest cover. The Aripo River had a slightly higher average nitrate level in both seasons with several peaks in the levels during the dry season. Cluster Analysis The analysis of correlation between parameters shows that the rivers separate quickly into two natural groupings (Figure 2). The first group consists of the St Joseph and Tacarigua Rivers. The St Joseph River is characterized by residential development high in the catchment, which becomes even more dense in the lower catchment. The Tacarigua River on the other hand while having significant areas of forest in the upper catchment, also has significant agricultural activity high in the watershed. Both these rivers are characterized by particular poor water conditions in their lower sites being mostly anoxic, particularly in the dry season when low flow conditions exist. The second grouping includes the other five rivers that are further sub-grouped into the Arouca River, the Guanapo-Arima-Aripo Rivers and the San Juan River. The Arouca River is similar to the Tacarigua River in having agricultural activity high in the watershed. However, the lower site was much less polluted that the Tacarigua River lower site. This may be due to the absence of significant point sources such as non-functional STPs in this catchment when compared to the Tacarigua River site. The presence of a non-functional STP a few kilometers upstream of the Tacarigua lower site had a significant effect on water quality. The second grouping is characterized by rivers with higher levels of forest cover. Arima has large areas of intact forest due to the efforts of the ASA Wright Nature Centre the largest landowner in the Arima valley. The Guanapo valley during the course of the study was largely undeveloped with the exception of former cocoa estate land. The Aripo River, while included in this grouping has significant levels of animal husbandry in the middle catchment above the WASA intake. The effect of this is most apparent during low flow conditions particularly at the lower site. The San Juan River is separated from the other sites in this grouping and its position places it in a larger grouping of minor impacted sites. This is an anomaly in that the San Juan River has

significant residential development in the upper catchment. However, unlike the St Joseph and Tacarigua Rivers it may not have strong point sources that are responsible for pollution of the river. However, the distance of the St Joseph-Tacarigua group and the San Juan River on the Cluster Tree should not be taken as strong dissimilarity.

Figure 2: Cluster Tree of rivers

Discussion These streams show varying levels of perturbation but more importantly, the potential for future deterioration of water quality with present land use trends. Implementing various management strategies can mitigate the poor water conditions in these streams. The importance of these streams to water flows in the Caroni River (particularly above the raw water intake) and to recharge of aquifers must be stressed.

The zoning laws that determine the areas in upper watersheds that development can take place are guided by physical conditions set out in legislation. The protection of natural areas for the provision of services such as surface water and ground water flow are not considered in terms of planning and development. The responsibility for watershed management is then spread between Government Departments such as the Ministry of Planning, Ministry of Agriculture, Land and Marine Resources and the Ministry of Public Utilities and the Environment. The fragmentation of responsibility for watershed management has led to fragmentation o measures in protecting watersheds and providing water for ecological processes and human communities. There is a need for the centralization of watershed management through memorandums of understandings (MOUs) or designation of specific responsibility. The further development of catchments particular in the upper watershed may decrease the potential of these areas to provide surface water of a quantity and quality needed for water provision. Poor low flow conditions in the Caroni River has lead to shut down of the Caroni Arena facility for short periods. Often linked to a particular pollution event, the overall deterioration of water quality may be masked. There will always be the demand for middle-class to upper class housing in river valleys in Trinidad. The river valleys to the west of the Caroni River Basin have been largely developed for housing and this trend seems to be moving eastwards. There must be enforcement of zoning laws to prevent development in the upper catchment, which is of especial importance where water is abstracted. The rivers of Trinidad (and Tobago) are used in planning for the routing of surface water drains including household ‘grey water’ as a low cost liquid waste receiving and transportation system. The continued use of these rivers in waste management can lead to further deterioration of water quality. The use of centralized sewerage systems and tertiary treatment for sewage may help protect the watercourses for future sustained use. A more holistic view of the water cycle must be taken where surface water, ground water and aquifer recharge must be viewed together and linked to more sustainable waste management. While, disincentives such as fines for water pollution in proposed legislation are the most likely strategies to be used for water management, incentives to developers for maintaining tree cover in watersheds and proper sewerage systems for water protection should be studied. The occurrence of agricultural practices in the catchments particularly the Tacarigua, Arima and Aripo Rivers mean that more emphasis must be placed on sustainable agricultural practices within these catchments. An up to date agricultural census can determine the level of agricultural activities in watersheds. From this point, strategic management of catchments with incentives for agro forestry and tree crops used in place of short-term crops would go a long way in maintaining the water quality and quantity of the rivers in the Caroni River Basin. The types of agricultural practices can be monitored within these areas. Where animal husbandry is practiced the mitigation measures must be put in place to deal with waste products from the operation. This would mean the proper disposal of waste products and the management of application of fertilizers in the field which can be accomplished by the physical measures in place to capture and the prevention of poor agricultural practices that lead to soil loss and siltation, the effective use of fertilisers, the upgrade of existing sewage treatment plants and the future development of centralised sewage treatment facilities can all aid in improvement of water quality.

The importance of these systems and the need for forest to be maintained on these catchments must be the focus of management plans for these areas (Faizool 2002). A holistic plan tha t takes into account all the functions of these systems must be put in place to maintain the supply and quality of water. Acknowledgements The work described in this paper was part of a larger study funded by the Dean’s Award for Research, UWI St. Augustine. I would like to thank Mrs Sharda Surujdeo-Maharaj for the GIS map she provided and Dr. Ian Ramjohn for assistance with the statistical analysis. LITERATURE CITED Bervoets Lieven, Marc Baillieul, Ronny Blust, and Rudolf Verheyen. 1996. Evaluation of effluent toxicity in a polluted lowland river. Environmental Pollution. 91 (1992) 333-341 Billett , M.F., and M.S. Cresser. 1992. Predicting stream-water quality using catchment and soil chemical characteristics. Environmental Pollution. 77 (1992) 236-268 Cuffney, Thomas F., J. Bruce Wallace, and Jackson R. Webster. 1984. Pesticide manipulation of a headwater stream: invertebrate responses and their significance for ecosystem processes. Freshwater Invertebrate Biology 3(4) DHV Consultants BV, Delft Hydraulics and Lee Young and Partners. 1999. Water resources Management Strategy for Trinidad and Tobago. Ministry of Planning and Development , Government of Trinidad and Tobago Faizool, Sheriff 2002 Watershed Management of the Northern Range in Trinidad and Tobago. paper presented to Natural Resources Management Unit, Organization of Eastern Caribbean States. Fore, Leska S., and James R. Karr. 1996 Assessing invertebrate responses to human activities: evaluating alternative approaches. J. N. Am. Benth Soc. 15(2) 212-231. Hatakeyama, Shigehisa, Hiroaki Shiraishi and Norio Kobayashi. 1990. Effects of aerial spraying of insecticides on nontarget macrobenthos in a mountain stream. Ecotoxicology and Environmental safety. 19 254-270 Reynolds B., S.J. Ormerod and A.S. Gee. Spatial patterns in stream nitrate concentrations in upland Wales in relation to catchment forest cover and forest age. Environmental Pollution. 84 (1994) 27-33 Stevens P.A., T.G. Williams, D.A. Norris, and A.P. Rowland. Dissoled inorganic nitrogen budget for a forested catchment at Beddgelert, North Wales. Environmental Pollution. 80 1-8

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