N. G. Gogate

Abstract: Anthropogenic alterations have affected urban hydrology in India and have generated a wide range of hydrological problems. Such alterations include increase in directly-connected impervious cover thus reducing natural groundwater recharge. In the past urban runoff was largely viewed as a nuisance, but within the new paradigm of sustainability, this water is recognized as a potential resource. This research paper discusses the importance of managing stormwater sustainably by recharging groundwater sources. It indicates the potential of stormwater harvesting, when properly managed, as a tool to counter depleting water sources and ever-increasing demand for water. The present study aims at developing a potential stormwater recharge zone map for a sub watershed in Pune city, India using GIS. Five classes of thematic maps have been integrated to prepare the final map. Each class is assigned a weightage depending on its influence on the recharge of stormwater. The resultant map (potential stormwater recharge zone map) thus prepared is classified into four classes: Very good, good, moderate and poor.

Abstract: This paper addresses the problem of selecting the most sustainable stormwater management alternative in developing countries in a dense urban context. Firstly, suitable Low Impact Development (LID) stormwater management measures for dense urban areas in developing countries were identified based on critical review of literature. Alternatives have been formulated as varying percentages (degree of adoption) of these suitable measures to manage the stormwater sustainably. Further, a novel decision-making framework is developed which generates the hierarchy for selection of the most sustainable stormwater management alternative. Four main criteria (technical, economic, environmental and social) comprising three quantitative and eight qualitative indicators have been used for evaluating seven alternatives. The regional and local societal priorities are captured through criteria-weightings and are translated into a decision-making methodology. Experts' opinions have been included using Analytical Hierarchy Process (AHP). One of the most widely used Multiple Attribute Decision-Making (MADM) method, TOPSIS, is used to rank the alternatives and to identify the most sustainable alternatives. Various scenarios to represent different stakeholders' perspectives have been articulated. Alternative with medium level of cost implication and satisfactory level of performance is chosen by the decision making method in most of the scenarios. The proposed decision making approach can be used for selecting sustainable stormwater management options in densely populated areas of developing countries.

Abstract: The implementation of sustainable urban drainage systems (SUDS) is increasing due to their advantages, which transcend runoff control. As a result, it is important to find the appropriate SUDS locations to maximize the benefits for the watershed. This study develops a multiscale methodology for consolidated urban areas that allows the analysis of environmental, social, and economic aspects of SUDS implementation according to multiple objectives (i.e., runoff management, water quality improvements, and amenity generation). This methodology includes three scales: (a) citywide, (b) local, and (c) microscale. The citywide scale involves the definition of objectives through workshops with the participation of the main stakeholders, and the development of spatial analyses to identify (1) priority urban drainage sub-catchments: areas that need intervention, and (2) strategic urban drainage sub-catchments: zones with the opportunity to integrate SUDS due the presence of natural elements or future urban redevelopment plans. At a local scale, prospective areas are analyzed to establish the potential of SUDS implementation. Microscale comprises the use of the results from the previous scales to identify the best SUDS placement. In the latter scale, the SUDS types and treatment trains are selected. The methodology was applied to the city of Bogota (Colombia) with a population of nearly seven million inhabitants living in an area of approximately 400 km2. Results include: (a) The identification of priority urban drainage sub-catchments, where the implementation of SUDS could bring greater benefits; (b) the determination of strategic urban drainage sub-catchments considering Bogota’s future urban redevelopment plans, and green and blue-green corridors; and (c) the evaluation of SUDS suitability for public and private areas. We found that the most suitable SUDS types for public areas in Bogota are tree boxes, cisterns, bioretention zones, green swales, extended dry detention basins, and infiltration trenches, while for private residential areas they are rain barrels, tree boxes, green roofs, and green swales.

Abstract: Groundwater plays a critical role to the total water resource potential of the Philippines especially in areas where there is low rainfall and where surface water is not readily available for agriculture and domestic use. However, during the past decades, groundwater depletion and pollution have been evident in many parts of the Philippines. This has led to excessive groundwater extraction that resulted to the lowering of the groundwater at an alarming level. This problem was further aggravated by rapid urbanization in most parts of the country that drastically affected the natural recharge of the land. Hence, this study is aimed to identify potential sites for artificial groundwater recharge in selected watersheds of Mount Makiling Forest Reserve (MMFR) that can enhance sustainable yield and promote conservation and storage of excess water. It utilized several factors in identifying the artificial groundwater recharge sites. These include infiltration and percolation qualities (slope, soil, geology, geomorphology, land cover, aquifer transmissivity, drainage density, and lineaments), water quality (electrical conductivity), and water storability (depth to groundwater). Each factor was reclassified based on their potential for artificial groundwater recharge and was ranked based on their influence on groundwater movement using Analytical Hierarchy Process (AHP). The suitability scales used in the reclassification were very poor, poor, moderate, good, and very good. Seven specialists from various fields of study including engineering, hydrology, geology, and forestry contributed their knowledge on groundwater recharge through pair-wise comparison. The results of the AHP showed that aquifer transmissivity is the most important factor and is given a weight of 15.9%. On the other hand, soil is given the least importance with a weight of 7.5%. These results were used to process the final potential map which integrated all the thematic maps using weighted overlay. The results of the potential map showed that majority (83.97%) of the site is moderately suitable for artificial groundwater recharge. The good, moderate, and poor suitable sites have 2180.03 ha, 12,274.39 ha, and 162.81 ha, respectively. Among the four watersheds in MMFR, Sipit Watershed has the largest cover of good suitable sites at 1288.68 ha or 59.11% of the entire study site. Meanwhile, the Tigbi Watershed has the least coverage of good sites with an approximate area of 54.46 ha only. In general, majority of these suitable sites for artificial groundwater recharge were found in sites that have high infiltration capacity and very acceptable water quality. It was also observed that the identified suitable sites were mainly located in cropland areas.

Abstract: As an essential component for the development of the Xiong’an New Area, China’s second capital, groundwater in the area has been overexploited, resulting in ecological and environmental geological problems Therefore, artificial groundwater replenishment measures are urgently required, for which the evaluation of the recharge potential is an important prerequisite In this study, a GIS (Geographic Information System)-based multi-criteria evaluation system was constructed, considering the source water conditions, recharge infiltration conditions, aquifer storage conditions, and environmental conditions In addition, factors such as the distance to a canal, source water quality, slope, vadose zone infiltration rate, drainage density, groundwater depth, aquifer hydraulic conductivity, aquifer thickness, groundwater quality, soil quality, and distance to sensitive areas were also analyzed GIS was used to draw and calculate potential artificial recharge sites The results showed that the potential recharge sites in the study area are mainly distributed in the alluvial plains on both sides of the river, with a total area of 21039 km2, accounting for 158% of the total study area In the Xiong’an New Area, the potential sites are mainly distributed in the alluvial–proluvial plains on both sides of the Baigou River in the north-central area, with a total area of 394 km2, accounting for approximately 22% of the total area of the Xiong’an New Area

Abstract: The present study is an attempt to model the stormwater quality of a stream located in Pune, India. The city is split up into twenty-three basins (named A to W) by the Pune Municipal Corporation. The selected stream lies in the haphazardly expanded peri-urban G basin. The G basin has constructed stormwater drains which open up in this selected open stream. The runoff over the regions picks up the non-point source pollutants which are also added to the selected stream. The study becomes more complex as the stream is misused to dump trash materials, garbage and roadside litter, which adds to the stormwater pollution. Experimental investigations include eleven distinct locations on a naturally occurring stream in the G basin. Stormwater samples were collected for twenty-two storm events, for the monsoon season over four years from 2018–2021, during and after rainfall. The physicochemical characteristics were analyzed for twelve water quality parameters, including pH, Conductivity, Turbidity, Total solids (TS), Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Bio-chemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Dissolved Oxygen (DO), Phosphate, Ammonia and Nitrate. The Water Quality Index (WQI) ranged from 46.9 to 153.9 and from 41.20 to 87.70 for samples collected during and immediately after the rainfall, respectively. Principal Component Analysis was used to extract the most significant stormwater quality parameters. To understand the non-linear complex relationship of rainfall characteristics with significant stormwater pollutant parameters, a Support Vector Regression (SVR) model with Radial Basis Kernel Function (RBF) was developed. The Support Vector Machine is a powerful supervised algorithm that works best on smaller datasets but on complex ones with the help of kernel tricks. The accuracy of the model was evaluated based on normalized root-mean-square error (NRMSE), coefficient of determination (R2) and the ratio of performance to the interquartile range (RPIQ). The SVR model depicted the best performance for parameter TS with NRMSE (0.17), R2 (0.82) and RPIQ (2.91). The unit increase or decrease in the coefficients of rainfall characteristics displays the weighted deviation in the values of pollutant parameters. Non-linear Support Vector Regression models confirmed that both antecedent dry days and rainfall are correlated with significant stormwater quality parameters. The conclusions drawn can provide effective information to decision-makers to employ an appropriate treatment train approach of varied source control measures (SCM) to be proposed to treat and mitigate runoff in an open stream. This holistic approach serves the stakeholder’s objectives to manage stormwater efficiently. The research can be further extended by selecting a multi-criteria decision-making tool to adopt the best SCM and its multiple potential combinations.