Hydrologic Footprint Research Articles

A collaborative hybridity design approach: enhancing urban water resilience and spatial legibility

ABSTRACT Within the global transition to sustainable urban water management, Dutch polder cities are also contemplating revitalising their water traditions. One of the keys to this task is to integrate water management into urban design, which is explored but not yet practically instrumentalized in the urban design process. This article introduces the concept of hybridity and develops a Hybridity Design Approach as an interdisciplinary methodology to explore the possibility of realising the extreme low impact Closed City Concept. Integration of the water environment and urban space needs interdisciplinary cooperation and sharing knowledge, as well as an innovative way of thinking about water-resilient urban design, maximising the landscape quality of a polder city while minimising its hydrological footprint in the region. Effective visualisation tools and techniques for this collaborative design process are developed and tested in the area of Zevenkamp in Rotterdam.

Numerical Experiments on Low Impact Development for Urban Resilience Index

Low impact development (LID) has become one of the strategies that effectively mitigate the impacts of climate change. In addition to the ability to reduce nonpoint source (NPS) pollution caused by flash floods from the surface runoff, LID has also been applied to control water quantity under extreme rainfall events. Due to the fact that studies about LID configuration optimization tended to control water quantity and gradually ignored the main functions of water quality treatment, this study aims to consider water quantity and quality to estimate the benefits and optimal configuration of LID by Non-Dominated Genetic Algorithm (NSGA-II). In addition, regarding to the outlet peak flow, hydrologic footprint residence (HFR) was considered to be the water quantity indicator due to the ability to represent the dynamics of flow changes, and the modified quality indicator (Mass Emission First Flush ratio, MEFF30) was corrected to represent the pollutant transport process in a large catchment area. The results show that the flood and MEFF30 reduction rate of LID are inversely proportional to rainfall duration and intensity. The benefit of pollutant reduction, which can still be maintained by 20% and 15% under a big return period and the long duration was about three times than the quantity control. Taking the cost into account, although the rain barrel had the best effect of reduction per unit area, green roofs and permeable pavements had a higher unit cost reduction rate due to the lower costs. The upper and middle reaches of the open channel and the confluence of rainwater sewers should be the optimal LID configuration to achieve the benefits of both flood and pollution reduction.

Evaluation of a Multi-Objective Genetic Algorithm for Low Impact Development in an Overcrowded City

Sustainability and resilience are up-to-date considerations for urban developments in terms of flood mitigation. These considerations usually pose a new challenge to the urban planner because the achievement of a sustainable design through low impact development (LID) practices would be affected by the selection and the distribution of them. This study proposed a means to optimize the distribution of LIDs with the concept of considering the reduction of the flood peak and the hydrologic footprint residence (HFR). The study region is a densely populated place located in New Taipei City. This place has been developing for more than 40 years with completive sewer systems; therefore, the design must consider the space limitations. The flood reduction induced by each LID component under different rainfall return periods was estimated, and then the detention ponds were also conducted to compare the improvements. The results showed that the performance of LIDs dramatically decreased when the return periods were larger than ten years. A multi-objective genetic algorithm (MOGA) was then applied to optimize the spatial distribution of LIDs under different budget scenarios, and to decide the priority of locations for the LID configuration. Finally, the Monte Carlo test was used to test the relationship between the optimal space configuration of LIDs and the impermeability of the study region. A positive correlation was uncovered between the optimal allocation ratio and the impermeable rate of the partition. The study results can provide general guidelines for urban planners to design LIDs in urban areas.

Genome-resolved metagenomics of an autotrophic thiocyanate-remediating microbial bioreactor consortium

Industrial thiocyanate (SCN−) waste streams from gold mining and coal coking have polluted environments worldwide. Modern SCN− bioremediation involves use of complex engineered heterotrophic microbiomes; little attention has been given to the ability of a simple environmental autotrophic microbiome to biodegrade SCN−. Here we present results from a bioreactor experiment inoculated with SCN− -loaded mine tailings, incubated autotrophically, and subjected to a range of environmentally relevant conditions. Genome-resolved metagenomics revealed that SCN− hydrolase-encoding, sulphur-oxidizing autotrophic bacteria mediated SCN− degradation. These microbes supported metabolically-dependent non-SCN--degrading sulphur-oxidizing autotrophs and non-sulphur oxidizing heterotrophs, and “niche” microbiomes developed spatially (planktonic versus sessile) and temporally (across changing environmental parameters). Bioreactor microbiome structures changed significantly with increasing temperature, shifting from Thiobacilli to a novel SCN− hydrolase-encoding gammaproteobacteria. Transformation of carbonyl sulphide (COS), a key intermediate in global biogeochemical sulphur cycling, was mediated by plasmid-hosted CS2 and COS hydrolase genes associated with Thiobacillus, revealing a potential for horizontal transfer of this function. Our work shows that simple native autotrophic microbiomes from mine tailings can be employed for SCN− bioremediation, thus improving the recycling of ore processing waters and reducing the hydrological footprint of mining.

Effect of meteorological conditions on onsite runoff control for reducing the hydrological footprint of green building

Rainwater management is an essential part of sustainable site of a green building, in which the complexity of meteorological conditions is a difficult problem to deal with. In this study, based on 20 year's daily historical records, five cities were selected to represent rainfall disparity between 50 state capitals of the United States of America. Then, the sites' hydrologic responses to different rainfall conditions were simulated over 30 year's hourly historical records, and the statistics of rainfall/runoff events were plotted into hydrological frequency curves to represent the site hydrology. The difference between different scenarios is reflected by comparing water balance and hydrological frequency curves. The results showed that average daily rainfall depth and average annual rainy days are two conditions with greatest effects on runoff potential. Retaining the 95–99th percentile rainfall event is required as design objectives for three sites to replicate predevelopment runoff characteristics, while even the 99th percentile was not enough for the other two sites, unless impervious cover reduced or the design storm doubled. Onsite runoff control minimized the impact of site development on runoff, but not on infiltration and evaporation. The sites evaporation increased from 1% to 11–36%. Besides, The distance between the obtained runoff frequency curve and the designed counterpart suggested that rainfall retained in situ was less than the design objective because of precipitation concentration, which is worthy of consideration in future research to reduce hydrological footprint of green building more economically and effectively.

The European 2015 drought from a hydrological perspective

Abstract. In 2015 large parts of Europe were affected by drought. In this paper, we analyze the hydrological footprint (dynamic development over space and time) of the drought of 2015 in terms of both severity (magnitude) and spatial extent and compare it to the extreme drought of 2003. Analyses are based on a range of low flow and hydrological drought indices derived for about 800 streamflow records across Europe, collected in a community effort based on a common protocol. We compare the hydrological footprints of both events with the meteorological footprints, in order to learn from similarities and differences of both perspectives and to draw conclusions for drought management. The region affected by hydrological drought in 2015 differed somewhat from the drought of 2003, with its center located more towards eastern Europe. In terms of low flow magnitude, a region surrounding the Czech Republic was the most affected, with summer low flows that exhibited return intervals of 100 years and more. In terms of deficit volumes, the geographical center of the event was in southern Germany, where the drought lasted a particularly long time. A detailed spatial and temporal assessment of the 2015 event showed that the particular behavior in these regions was partly a result of diverging wetness preconditions in the studied catchments. Extreme droughts emerged where preconditions were particularly dry. In regions with wet preconditions, low flow events developed later and tended to be less severe. For both the 2003 and 2015 events, the onset of the hydrological drought was well correlated with the lowest flow recorded during the event (low flow magnitude), pointing towards a potential for early warning of the severity of streamflow drought. Time series of monthly drought indices (both streamflow- and climate-based indices) showed that meteorological and hydrological events developed differently in space and time, both in terms of extent and severity (magnitude). These results emphasize that drought is a hazard which leaves different footprints on the various components of the water cycle at different spatial and temporal scales. The difference in the dynamic development of meteorological and hydrological drought also implies that impacts on various water-use sectors and river ecology cannot be informed by climate indices alone. Thus, an assessment of drought impacts on water resources requires hydrological data in addition to drought indices based solely on climate data. The transboundary scale of the event also suggests that additional efforts need to be undertaken to make timely pan-European hydrological assessments more operational in the future.

Evaluating Rainwater Harvesting System for School Buildings

Freshwater is becoming limited as our climate and weather pattern changes. In this study, a rainwater harvesting system was evaluated for collecting and utilizing rainwater for uses in non-potable purposes. Water-Balance was carried out for two design scenarios: Single tank and double tank, for irrigation in all main fields (202,724 ft2). The irrigation demand for the entire field was estimated to be about 1.08 million gallons on average after analyzing 14 years of data (2000-13). Installing a single tank of 210,000 gallon capacity was found to reduce the demand by 23%, whereas double tank installation was found to reduce the demand by about 10% on an annual basis. For these demand, irrigation needs has to depend on other sources such as city water supply or school’s retention pond. The cost-benefit analysis revealed that the system will have estimated initial cost of $85,000 (single tank installation). The corresponding annualized cost of ownership is $5,215 while projected savings on annual water bills is $6,079. The system could be paid off early, resulting in savings of about $45,000 for the life of the system. The system was found to benefit financially while contributing to the environment by conserving the freshwater from non-potable use and reducing hydrologic footprint by harvesting the stormwater runoff.

An evaluation of the Stormwater Footprint Calculator and the Hydrological Footprint Residence for communicating about sustainability in stormwater management

Low-Impact Development (LID) can enhance sustainability in stormwater management by attenuating excess runoff. Relevant technologies are typically implemented at individual lots and require the engagement of homeowners and developers. A new educational tool, the Stormwater Footprint Calculator (SFC), was developed to improve knowledge and change attitudes and behavior regarding stormwater sustainability. Similar to online carbon-footprint calculators, the SFC synthesizes a participant’s answers about lot and neighborhood-level land use and calculates hypothetical effects on instream flows, using hydrologic simulation. Participants receive feedback about their storm-water footprint using a new metric, the Hydrologic Footprint Residence (HFR), which measures the effect of urbanization on stream flow based on the duration and extent of flooding. An experiment was fielded to test the SFC as a tool for communicating about sustainable stormwater management and to compare the HFR against an orthodox stormwater metric, peak flow. A convenience sample of undergraduate students (N= 510) participated in the experiment. The results indicate that completing the SFC improves knowledge about the causes of stormwater runoff and LID technologies (although not about the effects of stormwater, which was already high among the students), and it influences intention to support sustainable stormwater management. The results also indicate that HFR provides a viable alternative to conventional engineering metrics for communicating a stormwater footprint and shows the value of online calculators for communicating complex civil engineering concepts.

Hydrologic Impact Assessment of Land Cover Change and Stormwater Management Using the Hydrologic Footprint Residence

AbstractUrbanization impacts the stormwater regime through increased runoff volumes and velocities. Detention ponds and low impact development (LID) strategies may be implemented to control stormwater runoff. Typically, mitigation strategies are designed to maintain postdevelopment peak flows at predevelopment levels for a set of design storms. Peak flow does not capture the extent of changes to the hydrologic flow regime, and the hydrologic footprint residence (HFR) was developed to calculate the area and duration of inundated land during a storm. This study couples a cellular automata land cover change model with a hydrologic and hydraulic framework to generate spatial projections of future development on the fringe of a rapidly urbanizing metropolitan area. The hydrologic flow regime is characterized for existing and projected land cover patterns under detention pond and LID‐based control, using the HFR and peak flow values. Results demonstrate that for less intense and frequent rainfall events, LID solutions are better with respect to HFR; for larger storms, detention pond strategies perform better with respect to HFR and peak flow.

Corporate social responsibility of regional institutions: save water and money with an ecological economics perspective in a climate change context

As ecological economic fundamentalists argue, we need a new paradigm for changing current global economic system basics. The real problem is that the limits of ecological economics are based on unrealistic or utopian objectives in the proposed research frameworks. Taking this problem into account, present research demonstrates that the combination of mixed methods creates valid results. In this case, the hydrologic footprint reduction method was created to achieve the main objective: to prove the usefulness of combining environmental science techniques along with economics tools. The most important result of the work is the relationships between export/import product balances in the Basque Country, Spain (among the three most important economic regions along with Cataluña and Madrid) and their implications in maximizing effectiveness in saving water and money thanks to external hydrologic footprint analysis. A comparison was made between global and local consumption patterns using the water footprint method. It demonstrated the importance of making small changes, which imply direct and indirect benefits for the economy and hydrologic resources.

Hydrologic Footprint Residence: Environmentally Friendly Criteria for Best Management Practices

The natural hydrologic flow regime is altered by urbanization, which can be mitigated through best management practices (BMPs) or low impact development (LID). Typically, the effectiveness of different management scenarios is tested by comparing post- and predevelopment instantaneous peak flows. This approach, however, does not capture the extent of hydrologic change and the effect on downstream communities. A new hydrologic sustainability metric is presented here to quantify the impact of urbanization on downstream water bodies on the basis of the inundation dynamics of the flow regime. The hydrologic footprint residence (HFR) is designed to capture both temporal and spatial hydrological changes to an event-based flow regime by calculating the inundated areas and duration of a flood. The HFR is demonstrated for a hypothetical watershed and a watershed on the Texas A&M University Campus, located in College Station, Texas. For the campus watershed, three design storms (2-, 10-, and 100-year) and a set of historical events (during the period 1978–2009) are simulated for various management scenarios, representing predevelopment conditions, development on campus, BMP-based control, and LID-based control. The results indicate that the HFR can better capture alterations to the shape of the hydrograph compared with the use of the peak flow only.