Nutrient loading in water bodies is an undeniably important concept due to the various impacts that nutrient loads can have in water bodies. Water pollution takes many varied forms, with each form having distinctive but significantly harmful effects. Nutrient loading, as a form of water pollution is detrimental due to the negative impacts of various nutrients on the water bodies. Various impacts have been associated with nutrient loading, particularly in small water reservoirs whose sources are significant inflows bearing municipal and industrial wastes. Consequently, it has been observed through various studies that water reservoirs in small towns bear greater levels of nutrient loads compared to those in rural areas and forested areas. Moreover, nutrients deposited in water reservoirs also vary in amount and type depending on their sources. Besides the nutrients, sediments also contribute to the alteration of key features of reservoirs, namely the reservoir capacities. Efforts are therefore made by water management authorities to reduce the potential for sediment and nutrient inflow into water bodies through provision of disposal standards for industrial and municipal waste water.
The key nutrients that create the greatest menace to water quality management include: total carbon, phosphorus, nitrogen and dissolved oxygen. The impacts of these nutrients on the water quality as well as on the aquatic life forms are also varied. Moreover, the importance of these nutrients in the water reservoirs is also significant due to their contributions to the aquatic life forms available in the reservoir. For instance, free dissolved oxygen is required by aquatic life for respiration. In the absence of dissolved oxygen, life is impossible in the water bodies. Similarly, other nutrients also contribute either positively or negatively to the growth of aquatic life as well as to water quality standards. Phosphorus and nitrogen are more probable in water reservoirs receiving inflow from agricultural areas while dissolved oxygen is found in any water reservoir. It is however balanced in concentration due to the relationship between water temperature and the solubility of oxygen (Weiner and Matthews 92).
The objective of this paper is to analyze nutrient loading in various small town water reservoirs within Texas. It has been realized that while many studies focus on the general nutrient loading in water bodies, the focus on phosphorus, nitrogen and dissolved oxygen has been minimal. This paper will thus maintain its focus on these three nutrients. An experimental and theoretical approach to study will be adopted for the paper in order to obtain conclusive results on the subject. While this method is supposed to be effective, the study will be limited in scope due to its focus on a minimal time frame for the water analysis.
Reservoirs are meant for water preservation for various uses. Some of the uses associated with reservoir water include: domestic purposes, navigation and canalization. All these uses depend on the quality of water accessible from the reservoirs. While these uses require more stringent quality standards, these standards are difficult to attain without determining the quality of water in the reservoir. It is only after sampling and analyzing samples for various aspects of water quality that effective water treatment can be accomplished. More conventional pollution control measures such as sedimentation and filtration and chemical water treatment procedures are ineffective towards addressing some of the nutrient load issues in water reservoirs. It is therefore mandatory for the nutrient loads to be determined outside the conventional water treatment procedures and to understand the water qualities in order to determine the suitability of the water for the intended uses.
According to Lee and others (5690) the sources of nutrients in reservoirs vary in type as well as in magnitude. However, it is an undisputable fact that phosphorus and nitrogen constitute the most important nutrients in water bodies. Nutrient loads have several detrimental effects on water quality, which can be said to be degrading to the least. Effects such as increased eutrophication due to nitrogen and depletion of dissolved oxygen are all degrading to reservoir water quality. Excessive algal growth is also an important influence of nutrient growth in water bodies. While sediments only result in reduced reservoir capacity, the load of nutrients in reservoirs renders water from such bodies unusable for some important purposes such as domestic applications. The effect of sediments also contributes to the increase in concentration of nutrient loads. This is particularly due to the observable reduction in reservoir capacity, which makes the concentration of nutrients per unit volume higher in the reservoir assuming that the sources of water are of constant flow (Morrison and Colombo 3). It is therefore expected that reservoirs with high sediment influx will also register higher nutrient loads per unit volume compared to reservoirs where the sediment influx is low.
Besides the sediments, other factors that have been noted to contribute to variations in reservoir capacities include geological conditions and area water requirements. For instance, it is expected that in areas where the need is higher, higher capacity reservoirs will be built to cater for the community needs in water services (Gaur 82). The yields of phosphorus and nitrogen in various water reservoirs is said to be linked to the reservoir capacity in that the reservoir capacity determines the rate of water inflow. Reservoirs with higher inputs have higher nutrients loads while those from low input volumes have lower loads. Similarly, the load concentrations during high flow periods such as storms are also significantly high (Morrison and Colombo 4).
Preston and others (2) also recognize the impacts of nutrient loads on water reservoirs. According to these authors, the elimination of nutrients from point sources does not contribute effectively towards the reduction of nutrient load in the recipient water bodies. Moreover, the degradation of water in reservoirs is directly linked to the concentration of dissolved nutrients such as phosphorus which results in depletion of dissolved oxygen. This effect is recognized by Lee and others (5692) as being the precedent of higher pollution in waters linked to municipal and industrial waste inflows. urban and agricultural areas are supposed to contain higher nutrient loads compared to rural and/ or forested areas. Chemicals used in agricultural lands such as fertilizers contain high percentages of nitrogen and phosphorus compounds which leech into the soil and are absorbed by ground overflow water during rainy seasons. Some of these nutrients find their ways into water reservoirs where they increase the nutrient loads in the reservoirs (Preston and others 2).
The impacts of nutrient loads in water reservoirs are elaborated in depth by Weiner and Matthews (4) in the description of the effects of pollution on water bodies. The authors suggest that nutrient loads, like other forms of water pollution have the potential of causing detrimental effects on both the ecology and the public health in general. With regards to public health concerns, eutrophication and excess algal growth have been identified to be of key concern due to the possibility of water borne infections. Fungal and bacterial infections are linked to the level of unacceptable pollutants such as algae in water bodies, especially where such bodies are sources of water for domestic purposes (Lee and others 5692). This means that any water collected from reservoirs in which nutrients have been confirmed to be loaded has to be taken through efficient water treatment procedures to avoid raising issues of health. Moreover, impacts of ecological imbalance due to the increase in nutrient loads are also undeniable, resulting frequently in the loss of aquatic life. Weiner and Matthews suggest that water treatment poses a difficult challenge due to the problems associated with sampling (81).
In an intensive study carried out in three major lakes, Garg and Garg (556) confirmed that the level of eutrophication in the lakes was corresponding to the level of nutrient loads in the lake. Various species of algae were also observed to flourish in waters with high levels of pollution. Moreover, the more competent algal types seemed to flourish more than the weaker types which were left to compete for nutrients with the aquatic biota. The implication of this is that besides causing eutrophication and algal boom in water bodies, nutrient loads also result in greater competition due to the increase in the number of microorganisms in water bodies. An ecological imbalance is a perfect example of potential impacts of such excessive nutrient loads in water bodies (Garg and Garg 557). In addition to this, the authors also point out the relevance of dissolved oxygen in the ecological balance equation, with the conclusion that in waters with high phosphorus and nitrogen loads, oxygen tends to be depleted due to the high number of organisms who compete for the limited resource. In addition to this, Garg and Garg also found out that waters with high levels of nutrient loads also became habitable for pollution dependent microorganisms which are likely to cause diseases (557).
Data Collection Procedures
Data concerning the nutrient loads in various water reservoirs was collected through experimental strategies. The key objective was to determine the nutrient loads in the water reservoirs at the time of the study. Samples for testing originated from water reservoirs in the Texas towns of Allen, Edinburgh and Mission. These towns were chosen due to their low population sizes and low levels of industrial operations which make it probable that their water reservoirs do not serve above their capacities. Moreover, limited agricultural activity occurs in each of these towns.
While collecting this data, focus was placed on three key nutrients i.e. dissolved oxygen, phosphorus and nitrogen. Composite samples were collected from various water reservoirs. To make the composite samples, grab samples were collected from various points in each reservoir and then mixed to form a composite. The samples were then analyzed for the nutrients in focus. In order to determine the phosphorus and nitrogen concentrations, calorimetric procedures were used by the study. Samples were reacted with ionic mixtures and the resulting colors visually compared to color standards. The resulting matches related to the concentrations of nitrogen or phosphorus respectively depending on the color codes that were used. The concentrations were given in mg/ L of sample.
To collect data for dissolved oxygen loading, an oxygen probe was used. The oxygen probe works through a membrane electrode which records current as proportional to the concentration of dissolved oxygen in the sample. The concentration can then be converted to mg/ L for the dissolved oxygen.
Nutrient loading in water reservoirs in small towns in Texas showed values which cannot be linked to intensive eutrophication. Consequently, recorded observation showed that the reservoirs have significantly low levels of algal concentration in comparison to reservoirs in the bigger towns of Texas. Particularly, water reservoirs in Mission had only traces of both phosphorus and Nitrogen while Edinburgh had higher values of phosphorus than Allen and lower values of nitrogen loads. On the other hand, Allen had high values of both phosphorus and Nitrogen. All the reservoirs in the three towns had considerable amounts of dissolved oxygen owing to the low population of pollution dependent microorganisms.
The impacts associated with high nutrient loads in water reservoirs have been identified as including eutrophication, excessive algal growth and depletion of dissolved oxygen. While some of the studies analyzed showed in-depth information about each of these impacts, it is clear that the objective of each of the studies was aimed at showing how nutrient loading can result in a degradation of water in reservoirs. The impacts extend to the public health sector as well as to ecology. In terms of public health, nutrient loads have been found to result in increased vulnerability of water borne diseases. This is based on the argument that the negative impacts of nutrient loads such as eutrophication result in the pollution of waters which can then cause water borne diseases if not well treated. Moreover, the treatment of water for domestic and industrial use follows varying procedures, which may not allow for the testing of nutrient loads at times. What this implies is that for effective understanding of the impacts of nutrient loads in water reservoirs in small towns of Texas to be achieved, it is necessary for comparative studies into water quality to be carried out.
The key impacts associated with nutrient loads in water reservoirs have been identified from existing literature in order to be related to observations made during the study. These impacts are globally applicable to all water bodies, despite being more concentrated in low capacity reservoirs located in areas exposed to agricultural and urban wastes.
Despite not being rampant in small town water reservoirs, nutrient loading is a global concern for water bodies. The impacts associated with nutrient loading may not be clearly discernible at the onset of load increase but are bound to create detrimental impacts such as degradation of water in reservoirs, depletion of dissolved oxygen and increased competition among biota. The relationship between the water inflow volumes, sources of influx and the type of point sources was however not established since the studies town reservoirs were of significantly similar sizes. The study is thus limited in scope as well as due to the lack of a long term study approach. More research should therefore be carried out in these areas for comparative purposes.
Garg, Jaya and Hari Krishna Garg. “Nutrient Loading and its consequences in a lake ecosystem”. Tropical Ecology 3, 2(2002): 355-358.
Gaur, R. Basic environmental engineering. New Age International Publishers Ltd, 2008.
Lee, Taesoo, Xiuying Wang, Michael White, Pupsha Tuppad, Raghavan Srinivasan, Balaji Narasimhan and Darrel Andrews. “Modeling water quality loads in the reservoirs of the upper Trinity River Basin, Texas, USA”. Water 20. 7(2015): 5689 – 5704.
Morrison, Jonathan and Michael Colombo. “Surface water quality and nutrient loads in Nepaug Reservoir Watershed, North Western Connecticut, 1999-2001”. U.S Geological Survey Scientific Investigations Report 2006-5272. 2006
Preston, Stephen, Richard Alexander and Charles Crawford. “Factors affecting stream nutrient loads: a synthesis of regional SPARROW model results for the continental united States”. Journal of the American Water Resources Association. 2011.
Weiner, Ruth and Robin Matthews. Environmental Engineering 4th Ed. Butterworth- Heinemann, 2003.