Lakes as living labs
Priyanka Jamwal, Aparna Madamanchi, Shubha Ramachandran, Suma Rao, Veena Srinivasan
Bengaluru has a Polluted Lakes Problem
Over the past three decades, lakes in Bengaluru (Bangalore) have witnessed a rapid shift decline as the city’s population grew from 4 to 10 million from 2000 to 2012. There are over 200 of these man-made structures, also called keres ( “kay-ray”). Historically, they were primarily used to store rainwater for irrigation and domestic purposes.
As the city grew, sewerage infrastructure has lagged. This has led to the widespread release of untreated and partially treated wastewater (industrial and domestic) into many of the lakes. Even lakes receiving treated effluent from STPs still face issues related to bird deaths, cyanobacteria blooms, fish kills, and water hyacinth growth due to high nutrient levels.
Citizens are playing an active role in rejuvenating lakes
Even as Bengaluru’s lakes have become polluted, citizen awareness and interest in addressing the problem have increased. Bengaluru has one of the most active citizen communities in India. There are some forty active citizen lake groups, working on the rejuvenation and restoration of lakes.
Citizen groups play many roles, including inter-agency coordination and fostering community awareness. Citizens however also play a crucial role in actually addressing lake pollution. They build constructed wetlands, raise funds for aerators and collaborate with agencies to experiment with new techniques like enzymes and Bokashi balls, to address critical lake health problems like cyanobacterial blooms and fish kills or aesthetic concerns like the look and smell.
Current intervention design is not science-based, because science itself doesn’t offer clear answers
Often, though, the techniques attempted are not rooted in science. They may be old wives tales or temporary solutions, wherein the problem recurs in a month or two. But the bottleneck is not necessarily ignorance. A bigger problem is that science itself is not positioned to offer clear answers.
The science is fragmented and there are gaps
Often scientific knowledge exists but it is fragmented across different scientific communities or disciplines that study different aspects of lakes; for instance, fish ecologists might understand trophic chains, limnologists might understand nutrient cycles and environmental engineers might have insights on water quality and how wetlands alter it. Each discipline holds a piece of the puzzle, but no one scientist has the complete picture and they don’t collaborate.
Moreover, the different disciplines often use different terminology and units so very little cross-learning occurs. And then there are gaps — questions that no one has answered — that must be filled before the viability of interventions and the possibility of unintended consequences can be assessed.
The science is not solution-oriented
The intent of science is to extend knowledge of fundamental processes, not to solve problems. First, problem definition may not be sharp enough, so many interventions address the wrong problem altogether. Second, many studies don’t account for confounding factors found under rapidly evolving field conditions, so solutions that work well under lab/controlled conditions often don’t work as intended in field conditions. And third, there is a dearth of studies in Indian conditions (tropic climate, high nutrient loading, monsoonal climate). So the bridge required to go from an understanding of nutrient cycles to solution design is incomplete.
For instance, one study by ATREE showed that constructed wetlands are not sinks but rather the source of inorganic nutrients like Nitrogen and Phosphorous into the lake. While Nitrogen (N) can be removed by the denitrification process, Phosphorous (P) removal can only be facilitated by physical removal (sedimentary cycle). So interventions that focus only on N miss the fact that P is the nutrient that drives eutrophication.
Much more research is needed on P removal in floating islands and the relative importance of physical (sedimentation) and biological processes (biofilms in the root zone), and how to maintain P uptake by regular harvesting of plants. As most peer-reviewed studies have taken place in low nutrient temperate systems, it is particularly important to understand P uptake potential in tropical urban hydrological systems.
The science is not settled
Another challenge is that the few published studies that do exist sometimes reach contradictory conclusions depending on which parameters they measured and what the conditions of the study were. For instance, there is a wide variation in the estimates of P-uptake by constructed wetlands, making it difficult to conclusively design solutions.
Additionally, when interventions don’t work as anticipated, the insights from real-world implementations never feed back into scientific inquiry — there is no cycle of learning. The framing of the science-society interface is uni-directional. Scientists frame study variables independent of what’s in the field.
“Lakes as living labs” is a science-based design approach
To address this conundrum, we suggest taking a “hypothesis-driven approach to intervention design” in polluted urban lakes. This involves setting up collaborations between researchers and practitioners who collectively treat the lake as a “living lab”.
The team hypothesizes how a solution would be expected to work based on the “best available science”, then sets up clear monitoring protocols to assess whether and how the solution is working. They track not just outcome variables and but “intermediate” variables as well. The whole case study is documented with the objective of drawing both scientific inferences and improving the next iteration of the intervention.
For instance, consider a constructed wetland design that hypothesizes that biofilms and root zone contribute much more significantly to P-uptake in floating wetland systems deployed in eutrophic lakes. This intervention would examine specifically the component of plant uptake to the overall removal capacity of floating islands, carefully computing all components of the P nutrient cycle.
We urgently need science-based approaches to solving pollution problems in lakes. However, we cannot wait for all the science to be “done” before a problem can be addressed. There are real costs to inaction and in any case, scientific knowledge is a moving target. Each study opens up new avenues for investigation (science is a never-ending quest), and each new field site brings in new confounding variables that have not been addressed previously. “Lakes as living labs,” is a systematic approach to solution design under such circumstances.
Jamwal, P., 2017. Fate of nutrients in human-dominated ecosystems. Resonance 22, 279–290.
Keizer-Vlek, H.E., Verdonschot, P.F.M., Verdonschot, R.C.M., Dekkers, D., 2014. The contribution of plant uptake to nutrient removal by floating treatment wetlands. Ecological Engineering 73, 684–690. https://doi.org/10.1016/j.ecoleng.2014.09.081
Verhofstad, M.J.J.M., Poelen, M.D.M., van Kempen, M.M.L., Bakker, E.S., Smolders, A.J.P., 2017. Finding the harvesting frequency to maximize nutrient removal in a constructed wetland dominated by submerged aquatic plants. Ecological Engineering 106, 423–430. https://doi.org/10.1016/j.ecoleng.2017.06.012
About the authors
Shubha Ramachandran and Suma Rao are with Biome Environmental Solutions, a Bangalore based NGO working on water issues.