Current World Environment

Introduction

Urbanization and population increase have resulted in variations in land cover and land use on a local to global scale. This process has the potential to significantly alter the structure and function of ecosystems¹. Although they make up only 2% of the planet's land area, cities create 78% of greenhouse gases, which has a substantial impact on global climate change. Because of the benefits that the oceans provide, including a food source, a means of transportation, a position that can be defended, and a healthy environment, humans have historically dwelt along the coast. Most main cities are situated along the coast, and halved of the global populations lives inside the hundred kilometres of sea.^2,3 Urban areas are a major source of the pollution that is putting strain on the seas and oceans. Waste water and sewage discharge from cities is one of the significant harmful approaches that cities contaminate coastal areas. Numerous cities around the coast release waste water, including sewage and industrial effluent, straight into the nearby rivers and seas. Improper disposal of plastics and other waste, contamination from household activities like using detergents and medications, untreated sewage and industrial wastewater containing chemicals and heavy metals, and urban storm water runoff that transports oil, grease, pesticides, and litter from streets and roofs. Because of pollution, habitat destruction, and overexploitation, the concentration of human populations close to the coast seriously damages freshwater supplies and aquatic ecosystems. These effects harm human health and marine biodiversity, disturb delicate coastal ecosystems, and deteriorate water quality.

The aquatic ecosystems that surround coastal communities, including estuaries, rivers, oceans, seashores, and coastal wetlands, have been heavily contaminated by pollution as a result of urbanization, industrialization, population increase, and differing farming practices. This leads to the deterioration of the environment. The sustainability of coastal environments is significantly hampered by pollution.⁴ Substantial industrial areas in the study region are found along the banks of the Gurupur and Nethravati rivers, which combine to form a single estuary before entering the Arabian Sea. Untreated home and industrial waste discharge and disposal into estuaries, rivers, nearshore waterways, and harbor operations are the main causes of coastal pollution in the study area.⁵ Two of the rivers that run westward in the Mangaluru coastline region are Gurupura and Nethravthi. The adjacent industries discharge a significant quantity of pollutants into them, which degrades the water's quality. For this research, seven surface water samples, including river water, were collected, for this investigation throughout the monsoon, pre-monsoon, and post-monsoon and subjected to established procedures for the analysis of multiple water quality indicators. Unplanned urbanization has significant continuing effects on both the human health and environment. Two particularly persistent and rapidly-evolving issues are air pollution from traffic smoke and water contamination from urban debris.⁶ In unplanned cities, access to safe drinking water is becoming increasingly difficult for residents, and municipal supplies are not always reliable. Groundwater supplies are also being impacted by sewage pipe leaks. Water shortages are something that most people deal with on a regular basis. Human waste and an inadequate sewage system, which are major causes of water pollution and seep into subsurface water sources, are significant factors that contribute to the impureness of the water in metropolitan areas.⁷ The release of domestic trash into water supplies is a practical aspect of urbanization, and this activity causes changes that impact the stability of the environment and the quality of the water for a variety of reasons. Urbanization, however, is one of the biggest issues groundwater planners face and one of the most detrimental elements affecting the quality of streams. Industrial waste give rise to a serious hazard to human health and water supplies. Aquatic creatures are negatively impacted by waste released from manufacturing processes, including untreated effluents, heavy metals, poisons, alkaline compounds, and contaminants.⁸ South Kanara, also known as Dakshina Kannada, is the 4866 square kilometer southern coastal district of the state of Karnataka. The district is situated between latitudes 120 57' and 130 50' north and longitudes 740' and 750' east. At its thinnest, it is around 177 kilometer length, 40 kilometer width, 80 kilometer width,⁹ and 20, 83,625 people are living there, according to the 2011 census. The Udupi district forms the district's northern boundary, to the east by the Shimoga, Chickmagalur, and Hassan districts, to the south by the Coorg district and the Kerala state's Kasaragod district, and to the west by the Arabian Sea. In addition to having the maximum literateness rate in Karnataka (88.62%).⁹ Dakshina Kannada district is well-known for its professional and higher education institutions as well as its banking industry. In Karnataka, it is second evenly more compactly district with a population,of 457 people per square kilometer. Over the past few decades, the seaside region of the Dakshina Kannada (DK) district has experienced incredible growth. This area expanded due to increased commercial activity with the establishment of a significant seaport in Panambur, as well as industry expansion as fertilizers, iron ore pelletization, and petrochemicals. Furthermore, it is anticipated that the planned establishment and growth of Mangalore's Special Economic Zones (SEZs) will accelerate the trend of development. Dakshina Kannada district has the second-highest number of registered vehicles in the state of Karnataka^. The number of registered automobiles is increasing annually by over 10%.¹⁰ The Regional Transport Office in Mangalore reports that approximately thirty thousand automobiles were registered in 2010 and 2011, while thirty-five thousand vehicles were registered in 2012 up until the month of March. 22,659 two-wheelers and 6,574 vehicles had been registered between June 2019 and May 2020, according to data from the regional transport office in Mangalore. There was a slight increase up until May 2021, when 7,957 cars and 25,702 two-wheelers were registered. The principal objective of this investigation is to know the influence of urbanization on water resources in Mangalore, along with specific objective, to collect water samples in different locations of Netravati and Gurupur River and to conduct standard laboratory tests for important water quality parameters and, to Analyze Water quality using WHO and BIS guidelines, weighed arithmetic Index method is employed to assess the urbanization impact on water quality.

Materials and Methods

Demography

According to the Census of India 2001, the urban area of Mangalore had citizens of 601 thousand in 2001, up from 44 thousand in 1901. The urban population growth of Mangalore from 1901 to 2001 is depicted in Figure 1. Between 1991 and 2001, there was a 4% annual increase in population growth, up from 1% between 1901 and 1911.

In 2011, 488,968 people called Mangalore home. Mangalore city has 488,968 residents, however there are 623,841 people living in its urban and metropolitan areas.

The city of Mangalore had 724,159 residents in 2021.¹⁰ A study conducted in 2011 on literacy rates in India found that 96.49% of men and 91.63% of women were literate.¹⁰

Six years old and younger made up about 8.5% of the population.¹⁰ In Mangalore city, 7726 people, or 1.55% of the total population, lived in slums.¹¹ Urban population growth in Mangalore shown in Fig 1.

Figure 1: Urban Population Growth in Mangalore, 1901–2021 Click here to view Figure

Methodology

The surface water samples from the locations (Fig 2) were collected from seven locations during the monsoon, before and after the year 2019 monsoon. July to September was taken as monsoon, and pre monsoon season from march to may, while October to December as the post-monsoon season. In accordance with the protocol recommended from APHA (American Public Health Association) (APHA, 2005),¹¹ total 84 surface water samples were collected. The methodology flow chart shown in Fig 2. The samples were drawn from the locations by using composite sampling methodology. Since water levels and depths vary with the seasons, rainfall, and location along the river, there is no single depth for the Netravati and Gurupur River; instead, the average depth, 1.5 m, is set for the duration of the study.

Figure 2: Flow Chart Click here to view Figure

Study Area

The research area shown in Figure 3 is the seaside area of the DK regionin the Karnataka state of India. It is positioned in between latitudes 12°45' N and 13°7'30" N and longitudes 74°45' E and 75° E. Nethravati and Gurpur are the study area's two principal rivers. We solely took into account the city's Central and Southern regions for our analysis. The quality assessment in this study was limited to Netravati and Gurupura River. The locations of the samples are shown in Table 1 in addition to longitude and latitude data, providing a brief overview of the sample locations.

Figure 3: Study area map of Mangalore showing the locations of samples. Click here to view Figure

Topography and Climate

The research area receives 3955 mm of rainfall on average annually, with 87% of that amount falling between June and September during the South-West monsoon. Temperature ranges from 17 to 37 degrees Celsius are typical for the tropical climate, which is also rather humid. Dense vegetation coexists with undulating topography in the research region. On top of friable sandstones and granitic gneisses is lateritic soil. On the banks of rivers, alluvial deposits are found. Sand accumulations make up the beaches. Mean fluctuation is between 6 and 7 m, and the average depth to the water table is between 7 and 9 m.

Results and discussions

The samples were drawn from the locations by using composite sampling methodology. Samples of surface water were taken throughout the monsoon, postmonsoon, and pre-monsoon seasons. Following extensive cleaning, 84 surface water samples were meticulously gathered in sterile polythene bottles, each of which was appropriately labeled. GPS coordinates were taken at each site to determine precise sampling positions, and after then, these coordinates were used to generate a sampling site map using Arc GIS 10.8. Every collected sample was analyzed in a lab, and the outcomes are compared with BIS and WHO guidelines. Weighted Arithmetic Index Method was used to calculate water’s WQI.¹²

Table 1: List of Surface Water Sampling Locations with Latitude and Longitude

Water quality analysis

Seventeen physicochemical parameters of water samples were analyzed utilizing the protocols outlined in Standard Methods (APHA, 2017).¹³ Table 2 shows the list of tests that were conducted as well as the methodology.

Table 2: Methods used for water quality analysis

WHO and BIS guidelines

There are two categories of water quality parameters, according WHO guidelines. Health criteria take into account chemical and radioactive components that have the potential to directly harm human health, while acceptance guidelines include characteristics that may not have any direct health consequences but cause an unpleasant taste or odor in the water (WHO 2017). The BIS water quality and World Health Organization's (WHO) recommendations are listed in Tables 3.¹⁴

Table 3: BIS and WHO Specification for Drinking Water (BIS- 10500: 2012), (WHO, 2017).

An important step in the growth of water assests is the analysis of water quality. Quality of Water can be described in terms of certain features of the water, typically physical, chemical, and biological (including bacteriological) that are significant for a particular service and that pose a hazard to human health if values beyond acceptable limits.¹⁵

The outcomes of water quality analysis in monsoon, pre monsoon and post monsoon months shown in the Table 4, 9, 12, 15, 18, 21 and 24.

The Descriptive Statistics of Water Quality Parameters of Gurupur River and Netravati River are Shown in Table 5, 10, 13, 16, 19, 22 & 25.

Temporal Distribution of water quality of Gurupura River and Netravati River by Weighted Arithematic Index Method are shown in Table 8, 11, 14, 17, 20, 23, and 26.

Graphical Variation of Reults of water quality anaysis of different sampling locations of Gurupura and Netravati River are shown in Figure 5 to 11.

Overall water quality analyis by Weighed Arithmetic Method of both Gurupura River and Netravati River, Before, during, and after the monsoon are shown in Table 27. Whereas Table 6 indicates the limitations of Weighted Arithmetic Index Method (WAI) Developed by Brown and co-workers in 1972.¹⁶

Table 4: Water quality analysis results for Surface water- Gurpur River (Kulur Bridge) (SW-01)

Figure 4: Results of water quality analysis for Surface water - Gurupur River (Kulur Bridge) from Nov 2018 to Sep 2019 Click here to view Figure

Table 5: Water Quality Parameter Descriptive Statistics for the Gurupur River (Kulur Bridge)

Tidal variations in the Arabian Sea have an influence on the Gurpur River's water quality at the time of sample station SW-01 (Kulur bridge) (Fig. 3). During the study period, the results of parameters like turbidity, iron, and EC exceeded the WHO and BIS guideline limits.

Table 6: Weighted Arithmetic Index Method

Calculation of Weighted Arithmetic Water Quality Index, (WAWQI) (Source- Brown et al. (1970).

Formula for the Overall Water Quality Index is

is employed to assess a water body's general quality using a variety of criteria.

The Weighted Arithmetic Water Quality Index (WAWQI) technique is the most commonly used approach.

There are three primary steps in the calculation:

Give every water quality metric a relative weight (Wn).

Based on each parameter's concentration in the sample, assign a quality rating (Qn) to it.

To obtain the overall WQI, add these values together.

First, give it a relative weight (Wn).

For the parameter used to calculate the unit weight (Wn), the value is inversely proportional to the recommended Standard value (Sn).

Wn = K/Sn where K is a proportionality constant.

According to drinking water regulations from an appropriate organization, such as the BIS or the WHO, Sn is the standard allowable value for the nth parameter.

K is computed as follows: K=1/E(1/Sn)

The value of guarantees that all weights added together equal one.

In step two,

find the quality rating (Qn = 100 × (Vn - Videal) / (Sn - Videal), where Vn is the water sample's estimated concentration of the n^th parameter. Videal is the parameter's optimal value for pure water.

This is zero for the majority of parameters.

There are notable exceptions.

PH: 7.0 is the optimal value.

The optimal level of dissolved oxygen (DO) is 14.60 mg/l.

The standard acceptable value for the n^th parameter is Sn.

Determine the Total WQI

A weighted sum of the quality ratings for each parameter divided by the total of their relative weights yields the final WQI value.

The formula becomes WQI = EWnQn as the sum of the weights (EWn) usually equals 1.

Water quality is then classified into a variety of categories (such as Excellent, Good, Satisfactory, Extremely poor, or Unsuitable) based on the final WQI score; however, the precise range definitions may differ depending on the index. Below, Nov 2018 Sample calculation are shown for reference.

Table 7: Results of Weighted Arithmetic Water Quality Index for November 2018 Samples

Table 8: Temporal Distribution of Water Quality of Gurupur River (Kulur Bridge) by Weighted Arithmetic Index Method

The above results (Table 8.0) shows that, the Water Quality of Gurupur river (Kulur Bridge) Vary from good to Unfit for the usage, based on the above results Gurupur River Water at Kulur Bridge can be used during monsoon and post monsoon.

Table 9: Results of Water Quality Analysis for Surface water- Gurpur River (Maravoor Bridge) (SW-02)

The electrical Conductivity EC and TDS values are not within the BIS guidelines and these two parameters are varied in the post- monsoon and pre- monsoon shown in the Table 9.

Figure 5: Results of water quality analysis for Surface water - Gurupur River (Maravoor Bridge) from Nov 2018 to Sep 2019. Click here to view Figure

Table 10: Descriptive Statistics of Water Quality Parameters for Gurupur River (Maravoor Bridge).

As per the Descriptive Statistics of Water Quality Parameters shown in the table 10, The Gurpur River's water quality at the sampling site SW-02 (Maravoor Bridge) (Fig. 5.0) meets the desirable limits of WHO and BIS guideline values during the study period. Only minor changes observed in Turbidity, DO, EC and Copper.

Table 11: Temporal Distribution of Water Quality of Gurupur River (Maravoor Bridge) by Weighted Arithmetic Index Method

The outcomes displayed in Table 11. Demonstrates that the Gurupur River's (Maravoor Bridge) water quality varies from excellent to good in throughout the year.

Table 12: Results of Water Quality Analysis for Surface water- Gurpur River (Gurpura Bridge ) (SW-03)