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Ambika Khadka
Department of Built Environment, School of Engineering, Aalto University, Finland

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Journal article
Published: 03 August 2021 in Journal of Hydrology
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The goal of Low Impact Development (LID) is to restore and maintain the pre-development flow regime. The static storage capacity, which is often used as a parameter in LID designs, provides the maximum capacity of an LID type and is easily quantifiable already at the design phase. However, the static storage approach does not consider the inter-event recovery of storage capacity by infiltration and evapotranspiration. This study investigated dynamic storage capacities of three stormwater management designs with increasing proportions of LID units on a 1.2 ha urban residential block in Southern Finland, to compare their cost-efficiency, as well as their potential in restoring the pre-development flow regime. The cost-efficiency of LID designs was assessed based on their ability to contribute to water losses, and on the additional construction costs required when comparing them to conventional solutions (e.g. asphalt replaced with permeable pavement). The design with a small storage capacity and a large capture ratio, i.e., the ratio of contributing area to LID area, was the least efficient albeit its small construction cost. The design with an appropriate balance between the capture ratio and the LID provided storage capacity was the most efficient option. In assessing the potential of stormwater designs in restoring the pre-development flow regime, the sum of infiltration and flow in storm sewer networks was more representative of the catchment total runoff than flow alone. Finally, an extensive simulation of a large set of differently placed LID units proved useful in a priori identification of the most influential units in the treatment train.

ACS Style

Ambika Khadka; Teemu Kokkonen; Harri Koivusalo; Tero J. Niemi; Piia Leskinen; Jan-Hendrik Körber. Stormflow against streamflow – Can LID-provided storage capacity ensure performance efficiency and maintenance of pre-development flow regime? Journal of Hydrology 2021, 602, 126768 .

AMA Style

Ambika Khadka, Teemu Kokkonen, Harri Koivusalo, Tero J. Niemi, Piia Leskinen, Jan-Hendrik Körber. Stormflow against streamflow – Can LID-provided storage capacity ensure performance efficiency and maintenance of pre-development flow regime? Journal of Hydrology. 2021; 602 ():126768.

Chicago/Turabian Style

Ambika Khadka; Teemu Kokkonen; Harri Koivusalo; Tero J. Niemi; Piia Leskinen; Jan-Hendrik Körber. 2021. "Stormflow against streamflow – Can LID-provided storage capacity ensure performance efficiency and maintenance of pre-development flow regime?" Journal of Hydrology 602, no. : 126768.

Research articles
Published: 25 December 2019 in Urban Water Journal
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Urbanization modifies the natural water cycle particularly by reducing the water storage capacity. We analysed the storage capacity of three stormwater management designs in south-western Finland to demonstrate how an urban catchment releases stormwater and how storage contributes to flood resilience. The analysis relies on EPA SWMM5.1 simulations of water balance for a seven-month period including two extreme rain events during the summer and autumn. The enhanced storage capacity provided by the designs increased resilience against flooding and released stormwater with slower rates leading to reduced peak flows. Even the design with the least storage (10% LID coverage) was efficient at regulating floods due to controlled flow in a vegetated swale, whereas the design with the highest storage capacity (60% LID coverage) demonstrated the possibility of restoring nearly natural water cycle in urban catchments. The study suggests storage capacity can act as a flood resilience indicator directly linked with the physical catchment characteristics.

ACS Style

Ambika Khadka; Teemu Kokkonen; Tero J. Niemi; Elisa Lähde; Nora Sillanpää; Harri Koivusalo. Towards natural water cycle in urban areas: Modelling stormwater management designs. Urban Water Journal 2019, 17, 587 -597.

AMA Style

Ambika Khadka, Teemu Kokkonen, Tero J. Niemi, Elisa Lähde, Nora Sillanpää, Harri Koivusalo. Towards natural water cycle in urban areas: Modelling stormwater management designs. Urban Water Journal. 2019; 17 (7):587-597.

Chicago/Turabian Style

Ambika Khadka; Teemu Kokkonen; Tero J. Niemi; Elisa Lähde; Nora Sillanpää; Harri Koivusalo. 2019. "Towards natural water cycle in urban areas: Modelling stormwater management designs." Urban Water Journal 17, no. 7: 587-597.

Original research article
Published: 24 September 2019 in Frontiers in Sustainable Food Systems
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Privately owned rangelands in the western US support many ecosystem services and are threatened by financial incentives favoring conversion to housing development and more intensive forms of agriculture. Recognizing this threat, the impact investment community has identified rangeland management as a potential investing strategy to produce financial returns while preserving or enhancing the ecosystem services provided by intact rangelands. This strategy is based primarily on the notion that a capital-intensive conversion from continuous to rotational grazing can financially sustain rangelands through a combination of increased productivity and potentially monetized ecosystem service flows. The potential for these gains is supported by compelling anecdotal evidence, yet a robust body of scientific literature based on rigorous field experiments has not supported those claims, nor produced transferrable estimates of the benefits provided by rotational grazing of livestock (particularly cattle in the western US). Therefore, to demonstrate investment viability and measure investment success, impact investors will likely need to address these well-documented disconnects through some combination of monitoring and process-based modeling. This study examines the extent to which existing modeling tools are up to this task, by assessing the ability of two process-based models to represent four specific rotational grazing benefits put forth by impact investors, using a ranch in northeastern Wyoming as a case study. Using the Soil Water Assessment Tool, we simulated high magnitude changes in the water balance from surface runoff to evapotranspiration, which may be a benefit or negative impact depending on context (Benefit 1). We simulated a decrease in soil water storage under rotational grazing, which directly contradicts the outcome assumed in investment literature (Benefit 2). Using the InVEST beta Rangeland Production Model (based on the Century ecosystem model), we simulated increased biomass productivity (Benefit 3) under rotational grazing, which enhanced animal performance under some management parameters but negatively impacted it in others (Benefit 4). We conclude that the impact investing community will likely find greater success through a shift to objective-oriented ranch management, rather than a specific focus on rotation, and will also need additional investment in science and monitoring to demonstrate benefits.

ACS Style

Beatrice L. Gordon; Virginia Kowal; Ambika Khadka; Rebecca Chaplin-Kramer; Roy Roath; Benjamin P. Bryant. Existing Accessible Modeling Tools Offer Limited Support to Evaluation of Impact Investment in Rangeland Ecosystem Services. Frontiers in Sustainable Food Systems 2019, 3, 1 .

AMA Style

Beatrice L. Gordon, Virginia Kowal, Ambika Khadka, Rebecca Chaplin-Kramer, Roy Roath, Benjamin P. Bryant. Existing Accessible Modeling Tools Offer Limited Support to Evaluation of Impact Investment in Rangeland Ecosystem Services. Frontiers in Sustainable Food Systems. 2019; 3 ():1.

Chicago/Turabian Style

Beatrice L. Gordon; Virginia Kowal; Ambika Khadka; Rebecca Chaplin-Kramer; Roy Roath; Benjamin P. Bryant. 2019. "Existing Accessible Modeling Tools Offer Limited Support to Evaluation of Impact Investment in Rangeland Ecosystem Services." Frontiers in Sustainable Food Systems 3, no. : 1.

Report
Published: 25 May 2019 in Hydrogeology Journal
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Though springs are the primary source of water for communities in the mid-hills of Nepal, an in-depth scientific understanding of spring systems is missing, preventing the design of effective climate-resilient interventions for long-term sustainability of springs. This study marks the first attempt to combine environmental isotopes analysis with hydrometric and hydrogeological measurements to identify dominant recharge zones for springs in two mountainous catchments—Banlek and Shikarpur—in Far-Western Nepal. In total, 422 water samples collected from rainfall, springs and streams between March 2016 and March 2017 were analyzed for their isotopic composition (δ18O and δD). Isotopic composition of rainwater shows seasonality, suggesting that different sources of water vapor cause rains in monsoon and in dry season. Rainfall responses of individual springs were used to identify connections to unconfined and deeper groundwater strata. The isotopic composition of springs in the two catchments ranges from −9.55 to −8.06‰ for δ18O and −67.58 to −53.51‰ for δD. The isotopic signature of the spring sources falls close to the local meteoric water line for the corresponding season, indicating strong rainfall contribution to springs. Altitudinal isotopic gradients suggest mean recharge elevation of 2,600–2,700 m asl for springs in Shikarpur, which lies beyond the surface-water catchment, and a recharge elevation of 1,000–1,100 m asl for Banlek, which partially extends beyond the surface-water catchment. The demarcated recharge zones will be used by government agencies to implement recharge interventions to increase the resiliency and reliability of springs in Far-Western Nepal. Bien que les sources constituent la principale source d’alimentation en eau pour les communautés situées au milieu des collines du Népal, il manque une compréhension scientifique approfondie du fonctionnement des sources, ce qui empêche de concevoir des interventions résilientes efficaces face au changement climatique, pour assurer la pérennité des sources. Cette étude marque la première tentative de combiner l’analyse des isotopes environnementaux et les mesures hydrométriques et hydrogéologiques pour identifier les zones de recharge dominantes des sources de deux bassins versants montagneux—Banlek et Shikarpur—dans l’Extrême-ouest du Népal. Au total, 422 échantillons d’eau prélevés dans les pluies, les sources et les cours d’eau entre mars 2016 et mars 2017 ont été analysés en fonction de leur composition isotopique (δ18O et δD). La composition isotopique de l’eau de pluie montre une saisonnalité, ce qui suggère que des sources différentes de vapeur d’eau provoquent les pluies en mousson et en saison sèche. Les réponses des sources individuelles aux épisodes pluvieux ont été utilisées pour identifier les connexions à des aquifères libres ou profonds. La composition isotopique des sources dans les deux...

ACS Style

Karthikeyan Matheswaran; Ambika Khadka; Sanita Dhaubanjar; Luna Bharati; Sudhir Kumar; Surendra Shrestha. Delineation of spring recharge zones using environmental isotopes to support climate-resilient interventions in two mountainous catchments in Far-Western Nepal. Hydrogeology Journal 2019, 27, 2181 -2197.

AMA Style

Karthikeyan Matheswaran, Ambika Khadka, Sanita Dhaubanjar, Luna Bharati, Sudhir Kumar, Surendra Shrestha. Delineation of spring recharge zones using environmental isotopes to support climate-resilient interventions in two mountainous catchments in Far-Western Nepal. Hydrogeology Journal. 2019; 27 (6):2181-2197.

Chicago/Turabian Style

Karthikeyan Matheswaran; Ambika Khadka; Sanita Dhaubanjar; Luna Bharati; Sudhir Kumar; Surendra Shrestha. 2019. "Delineation of spring recharge zones using environmental isotopes to support climate-resilient interventions in two mountainous catchments in Far-Western Nepal." Hydrogeology Journal 27, no. 6: 2181-2197.

Journal article
Published: 28 March 2019 in Sustainability
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Multifunctionality is seen as one of the key benefits delivered by sustainable urban drainage systems (SUDS). It has been promoted by both scientific research and practical guidelines. However, interrelations between different benefits are vaguely defined, thus highlighting a lack of knowledge on ways they could be promoted in the actual design process. In this research, multifunctionality has been studied with the help of scenario analysis. Three stormwater scenarios involving different range of SUDS elements have been designed for the case area of Kirstinpuisto in the city of Turku, Finland. Thereafter, the alternative design scenarios have been assessed with four criteria related to multifunctionality (water quantity, water quality, amenity, and biodiversity). The results showed that multifunctionality could be analyzed in the design phase itself, and thus provided knowingly. However, assessing amenity and biodiversity values is more complex and in addition, we still lack proper methods. As the four criteria have mutual interconnections, multifunctionality should be considered during the landscape architectural design, or else we could likely lose some benefits related to multifunctionality. This reinforces emerging understanding that an interdisciplinary approach is needed to combine ecological comprehension together with the system thinking into SUDS design, locating them not as individual elements or as a part of the treatment train, but in connection with wider social ecological framework of urban landscape.

ACS Style

Elisa Lähde; Ambika Khadka; Outi Tahvonen; Teemu Kokkonen. Can We Really Have It All?—Designing Multifunctionality with Sustainable Urban Drainage System Elements. Sustainability 2019, 11, 1854 .

AMA Style

Elisa Lähde, Ambika Khadka, Outi Tahvonen, Teemu Kokkonen. Can We Really Have It All?—Designing Multifunctionality with Sustainable Urban Drainage System Elements. Sustainability. 2019; 11 (7):1854.

Chicago/Turabian Style

Elisa Lähde; Ambika Khadka; Outi Tahvonen; Teemu Kokkonen. 2019. "Can We Really Have It All?—Designing Multifunctionality with Sustainable Urban Drainage System Elements." Sustainability 11, no. 7: 1854.

Conference paper
Published: 01 September 2018 in Smart and Sustainable Planning for Cities and Regions
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Low impact development (LID) has received significant attention in supplementing urban drainage designs. This study demonstrates the effects of LID-based urban designs on water balance components for an urban catchment. Two LID-based urban designs (A, B) are simulated for short term (E1) and long term (E2) periods and the effects of the various designs on different water balance components are assessed. The goal of the study is to demonstrate the performance of the designs to realize the sponge city concept. For the intensive short event, scenario A with 15% LID is not effective whereas scenario B with 49% LID is highly effective. For the longer period, both scenarios are highly effective in replicating sponge city concept. In addition, the A scenario possesses a potential for producing sponge city concept for rain events for return periods lower than 100 years.

ACS Style

Ambika Khadka; Teemu Kokkonen; Elisa Lähde; Tero Niemi; Nora Sillanpää; Harri Koivusalo. Effects of LID-Based Urban Designs on Water Balance. Smart and Sustainable Planning for Cities and Regions 2018, 68 -73.

AMA Style

Ambika Khadka, Teemu Kokkonen, Elisa Lähde, Tero Niemi, Nora Sillanpää, Harri Koivusalo. Effects of LID-Based Urban Designs on Water Balance. Smart and Sustainable Planning for Cities and Regions. 2018; ():68-73.

Chicago/Turabian Style

Ambika Khadka; Teemu Kokkonen; Elisa Lähde; Tero Niemi; Nora Sillanpää; Harri Koivusalo. 2018. "Effects of LID-Based Urban Designs on Water Balance." Smart and Sustainable Planning for Cities and Regions , no. : 68-73.

Articles
Published: 22 September 2015 in Water International
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The water resources of the Koshi Basin (87,311 km2) are largely untapped, and while proposals for their development exist, their impacts on current and future water demand are not quantified. The current study is the first to evaluate the impacts of 11 proposed development projects for hydropower generation and water storage. We find that 29,733 GWh of hydropower could be generated annually and 8382 million m3 of water could be stored. This could satisfy unmet demand in the current (660 million m3) basin situation and in future scenarios – i.e. population, agricultural and industrial growth – that are projected to have 920, 970 and 1003 million m3 of unmet demand, respectively, by 2050.

ACS Style

Pennan Chinnasamy; Luna Bharati; Utsav Bhattarai; Ambika Khadka; Vaskar Dahal; Shahriar Wahid. Impact of planned water resource development on current and future water demand in the Koshi River basin, Nepal. Water International 2015, 40, 1004 -1020.

AMA Style

Pennan Chinnasamy, Luna Bharati, Utsav Bhattarai, Ambika Khadka, Vaskar Dahal, Shahriar Wahid. Impact of planned water resource development on current and future water demand in the Koshi River basin, Nepal. Water International. 2015; 40 (7):1004-1020.

Chicago/Turabian Style

Pennan Chinnasamy; Luna Bharati; Utsav Bhattarai; Ambika Khadka; Vaskar Dahal; Shahriar Wahid. 2015. "Impact of planned water resource development on current and future water demand in the Koshi River basin, Nepal." Water International 40, no. 7: 1004-1020.