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Aquatic Procedia 4 ( 2015 ) 585 – 592

INTERNATIONAL CONFERENCE ON WATER RESOURCES, COASTAL AND OCEAN ENGINEERING (ICWRCOE 2015) Identification of potential sites for detention ponds along the Vrishabhavathi River

P T Aravindaa*,H B Balakrishnab,K C Jayaramuc

a*Government Engineering College Ramamagara, ,562159, bBangalore Institute of Technology, , Karnataka,560004, India cBangalore Institute of Technology, Bangalore, Karnataka,560004, India

Abstract

Vrishabhavathi Watershed is a constituent of the Basin, Bangalore Urban and Ramanagara District and covers an area of 360.620Km2, representing seasonally dry tropical climate. In Vrishabhavathi watershed Vrishabhavathi River is the main surface water source which is tributary of river Arkavathy, which joins the Cauvery River at a later stage. Earlier this surface water was mainly used for agricultural purpose and drinking purpose. The watershed lies in Bangalore urban and Bangalore rural area. The stream receives a lot of waste water released from industrial and domestic areas. The water is highly polluted and generates lot of foul smell in the flow stretch in urban region. An attempt has been made to identify the potential sites for detention ponds along the Vrishabhavathi River which will be used to maintain the acceptable water quality for sewage irrigation. For this analysis we need the thematic maps such as Base map, Drainage map, Land use /land cover map and Vrishabhavathi River geometry map. Remote sensing and GIS is useful to identify the sites for detention ponds along the river. By assigning the weights to point feature in Vrishabhavathi River geometry map, then calculating suitability indices potential sites for detention ponds are identified .The water stored in the detention ponds are continuously treated with minimum cost and allowed to flow in the downstream for further oxidation. At suitable location water can be used for sewage irrigation. © 20152015 The The Authors. Authors. Published Published by by Elsevier Elsevier B.V. B.V. This is an open access article under the CC BY-NC-ND license (Peerhttp://creativecommons.org/licenses/by-nc-nd/4.0/-review under responsibility of organizing committee). of ICWRCOE 2015. Peer-review under responsibility of organizing committee of ICWRCOE 2015 Keywords:Watershed, Urban catchment, Detention Pond, GIS, Sewage Irrigation.

* Corresponding author. Tel.: +0-000-000-0000 ; fax: +0-000-000-0000 . E-mail address: [email protected]

1. Introduction

River water pollution is the major global problem in an urban area. The quality of water is an important factor to be considered before it is used for domestic, industrial and irrigation purpose. Majority of industries in an urban area

2214-241X © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of ICWRCOE 2015 doi: 10.1016/j.aqpro.2015.02.076 586 P.T. Aravinda et al. / Aquatic Procedia 4 ( 2015 ) 585 – 592

are water based and a considerable volume of contaminated water will be discharged in to the river course from them (Puthenveeduhari kumar et al., 2014).With increasing population, the gap between the supply and demand of water is widening and is reaching such alarming levels that in some parts of the world it is posing a threat to human existence. It is a time, to refocus on one of the ways to recycle water through the reuse of urban wastewater, for irrigation and other purposes. In general, wastewater comprises liquid wastes generated by households, industries, commercial sources, as a result of daily usage, production, and consumption activities (Intizar Hussain et al., 2002). Andrew Bradford et.al. 2003 conducted studies on waste water irrigation in and around Hubli-Dharward region. In the present study the water quality of the Vrishabhavathi River is below the acceptable range (Aravinda et al., 2014). In the watershed Vrishabhavathi River is the major surface water source which is tributary of Arkavathy, which joins the Cauvery River. It drains Bangalore Urban area and is the outlet for the domestic and industrial wastes of that area. Earlier this river water was mainly used for agricultural and drinking purposes (Madhukar R et al., 2013). Since this watershed lies in Bangalore urban and Bangalore rural, today this water is not safe for agricultural activities, which is highly contaminated. There are so many major and minor industries functioning in the watershed. Major industries have adopted their own STP and treated water will be discharged in to the river. In the case of minor industries they directly pour untreated water in to the river. This leads to increase of contamination level in the Vrishabhavathi River. Deterioration of tanks and drains in the urban area is the main factor for urban flooding and change in water quality. There are only two treatment plants available along the length of the Vrishabhavathi River, which is not sufficient to reduce the pollution level. Hence an immediate action has to be taken for identification of potential sites for detention ponds and treatment plants along the river course. After treatment this water can be used for irrigation and other purpose.

2. Study Area

Vrishabhavathi Watershed is a constituent of Arkavathi River Basin, Bangalore Urban and Ramanagara District and covers an area of 360.620 Km2 (UTM WGS1984 43N) lying between latitudes 120 441 3711 to 130 21 3111 N and longitudes 770 231 1411 to 770 341 5911 E. Location Map of the Study area is shown in Fig.1.Vrishabhavathi River is perennial due to the contribution of domestic and industrial effluents. Graph.1. shows the average flow volume during past 5 years. (BWSSB Water quality data book 2009-2013)

Fig.1. Location Map of Study area Graph.1.Vrishabhavthi River flow volume during 2009-2013

P.T. Aravinda et al. / Aquatic Procedia 4 ( 2015 ) 585 – 592 587

3. Data Used and Methodology

To achieve the objective the following data is necessary. 1. The Survey of India Topographical map in 1:50000 2. Digitized Base Map and Drainage map in 1:50000 3. Google Earth Image 4. Land use/Land cover map

Base map of the study area is prepared by SOI topographical maps using ArcGIS 10, which shows major features such as major tributaries of river, major roadways, railway line and major tanks. With reference to Base map and SOI topographical maps identification of the all streams which contribute the water to main river course are done, which is known as Drainage map. Using morphometric analysis the total number of streams and drainage density were calculated. This gives an idea about the network of the drains in the watershed. Using field survey, the top width, bottom width and depth of the river course are determined at different points along the river course. The map showing the dimensions of the Vrishabhavathi river stretch was prepared. The cross sectional area was calculated at various locations in the course of the river. From the cross sectional area and length of the river stretch we get the volume of water in that particular stretch. In the Attributes of the map enter all the details related to the river dimensions. Identify the stretch having more width and more storage capacity of water. Using Land use/Land cover map identify the users of the treated river water. By Integrating Vrishabhavathi River geometry map, Google Earth Image and Land use/ Land cover map locate the potential sites for detention pond and waste water treatment plant. From the Treatment Plant water has to be supplied to the elevated Storage tank, which provides water for irrigation through channel by gravity. Fig.2 and Fig.3 shows Base map and Drainage map respectively.

Fig.2.Base map of Vrishabhavathi Watershed Fig.3. Drainage map of Vrishabhavathi Watershed 588 P.T. Aravinda et al. / Aquatic Procedia 4 ( 2015 ) 585 – 592

4. Identification of Suitable Location for Detention Ponds

The Detention pond has a permanent pool of water that fluctuates in response to precipitation and runoff from the contributing areas. It can be used for flood control and sewage water treatment (USEPA). For the present study, Vrishabhavathi River geometry map is prepared by the field survey data and Base map of the Vrishabhavathi River in the watershed. In this map we can see the point feature which shows the longitudinal section points at irregular intervals. For each point we have measured the top width, bottom width and maximum depth of flow. For the present study all the sections are considered as trapezoidal. In the curves we have measured the cross sectional area and volume by small segmental approach. All these details are entered in the attributes. In the Urban region already we have two treatment plants having capacity of 180 MLD of Primary and Secondary and 75 MLD of Tertiary in Rajarajeshwari Arch and Mylasandra respectively. Further there are no treatment plants along the river stretch. After Mylasandra again there are so many tributaries that will join the river which adds up industrial, Agricultural and domestic pollutants. Earlier this stretch of river water was used for irrigation purpose. The straight stretch of the river which is having sufficient length, width and proper storage for detention pond are identified. Then probable agricultural area, in the vicinity of the detention pond was located through GIS analysis. The quantity of water required for irrigation was calculated based on the crop type. After identifying detention ponds the treatment plant was proposed near the banks of river. Using Land use /Land cover map (KSRSAC) and Google earth image identify the barren land, industrial area, public parks, forest plantation area and agricultural area and its elevation, which is near to proposed detention pond location. From the treatment plant water will be transferred to the elevated storage tank located at a suitable place which satisfies the demand through gravity flow. The following parameters were considered for the identification of detention ponds along the river stretch.

1. Length of the River stretch 2. Width of the River stretch 3. Volume of water stored in that stretch 4. Space available for setting up of Treatment Plants 5. Elevated Place for Storage Water Tank 6. Agricultural Pattern Near to the Detention Pond

5. Analysis

The following analysis was done for the identification of Suitable locations for Detention Pond, Treatment Plant and Elevated Storage Tank. For all the parameters we have to assign the weightage based on its importance. Then these weightage factors were integrated using GIS software to identify the suitable locations. From the field survey data we got the length and width of the river stretch. 1 is the least value assigned for the parameter and 4 is the highest value. Parameter with weight 4 indicates that it is highly suitable. Table 1 and Table.2 shows the weights or weightage factor assigned for Length and Width of the River stretch. Fig.4 and Fig.5 shows the Weightage factor map for River Stretch length and Width.

Table 1.Weightage for Length of the River stretch Table 2.Weightage for Width of the River Stretch

Range of length of River Weightage factor Range of length of River Weightage factor Stretch (m) Stretch (m)

<10 1 < 100 1 10-20 2 100-200 2 20-30 3 200-300 3 >300 4 >30 4 P.T. Aravinda et al. / Aquatic Procedia 4 ( 2015 ) 585 – 592 589

Volume of water stored in the detention pond depends upon the depth of the water at various seasons of a year. Volume of water again depends upon the length and width of the river stretch. Depth of the water for assigning the weightage factors mainly depend upon the height of the bund for the detention ponds. For urban region we considered the safe depth of 1.5 m and for rural region it is 2m. If we provide more than 2 meters flooding occurs in the adjoining lands of river course. Table.3. shows weightage assigned for volume. Fig.6 shows Weightage map for River stretch volume.

Table 3. Weightage for Volume of water Table 4.Weightage for Space

Depth of the Water Weightage factor Area Weightage factor < 0.5 1 Settlement 1 0.5-1 2 Private Property 2 1-1.5 3 Barren/Fallow Land 3 >1.5 4 Govt Land 4

Space is the important criteria for the construction of Treatment Plants near to the Detention Pond. Government land and Barren land are most suitable for construction of Treatment plants. If it is private property or settlements then it will be a problem of re-habitation. Weights are assigned with reference to Land use /land cover and Google Earth Image. Table.4 shows weightage assigned for space availability for construction of treatment plant near the proposed stretch of the detention pond. Fig.7. shows the Weightage map for availability of space for treatment plant.

Table 5.Weightage for Elevated Place Table 6.Weightage for Land use Pattern

Distance from the Weightage factor Land Pattern Weightage factor Treatment Plant(km) Settlements 1 < 4 1 Forest Plantation 2 2-4 2 Agricultural Plantation 3 1-2 3 Kharif +Rabi 4 >1 4

Table 7.Weightage for Location of Detention Pond

Land Pattern Weightage factor Not Suitable 1 Less Suitable 2 Suitable 3 Highly Suitable 4 Elevated Storage tank place depends upon the distance from the treatment Plant. If distance is more supply cost will be more. If distance is less than 1km then that place is highly suitable. If it is not available then far off distance were also be considered. Its elevation must be more than the demand areas. Table.5 shows the weightage assigned for Elevated Storage Tank based on the distance from the treatment plant and the elevation. Fig.8. shows the Weightage for distance from the Treatment Plant to Elevated Storage tank. Land use pattern is mainly depending upon the activities of human being. Throughout the year water will be flowing in the river due to sewage water. Hence perennial crops and Kharif + Rabi are most suitable. Table.6 shows weightage assigned for landuse pattern. Fig.9. shows the weightage map for Land use pattern along the River Stretch.GIS analysis was done to prepare all the maps for all the parameters based on the weightage factor. The combination of other parametric weights resulted in the weightage factor map for the location of detention pond. Table.7 shows the weightage assigned for location of Detention Pond. Then all these maps are integrated in GIS environment to identify the suitable locations of the Detention Ponds. Fig.10. shows Suitable location map of Detention Pond, In line Treatment plant and Elevated 590 P.T. Aravinda et al. / Aquatic Procedia 4 ( 2015 ) 585 – 592

storage tank. Also generate integrated map of Land use pattern and Detention pond location map. Fig.11. shows the integrated map of Landuse pattern and Detention pond location in the River stretch. It shows the probable usage of water from the Detention pond.

Fig.4.The Weightage map for River Stretch length Fig.5.The Weightage map for Width.

Fig.6.The Weightage map for River Stretch volume Fig.7. The Weightage map for Space Availability P.T. Aravinda et al. / Aquatic Procedia 4 ( 2015 ) 585 – 592 591

Fig.8.The Weightage map for Elevation Storage Tank Fig.9.The Weightage map for Landuse Pattern

Fig.10.Suitable location map of Detention Pond Fig.11.Integrated map of land use pattern and and Inline Treatment Plant Location of Detention pond 592 P.T. Aravinda et al. / Aquatic Procedia 4 ( 2015 ) 585 – 592

6. Conclusion

Vrishabhavathi River was a source of holy water to the people lived in the early years. Eventually, urbanization has led to the deterioration of water quality and spoiled the surrounding environment. The aquatic life, the flora and fauna of the surrounding region has been completely destroyed. The present study was aimed at improving the water quality and utilizes the treated water for irrigation. About six parameters like length of the River stretch, Width of the River stretch, Volume of water stored in that stretch, Space available for setting up of Treatment Plants, Elevated Place for Storage Water Tank, and Agricultural Pattern Near to the Detention Pond. The GIS analysis has revealed different locations of detention pond which are to be constructed in the near future based on the ground survey and priority. In the beginning 3 inline treatment plants are required to reduce the burden on the treatment plant constructed near the detention ponds. Two detention ponds are required in the lower reaches where the suitable and highly suitable locations are identified. The treatment plants bring the water quality to the agriculture water quality standards. This will certainly bring down the water pollution and eradicates seasonal flood occurring at many places in the river stretch also.

Acknowledgement

Authors sincerely acknowledge the support extended by the officials of Bangalore Water Supply and Sewerage Board and Karnataka state Remote Sensing Application Centre, Bangalore, Karnataka state, India.

References

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