Lake Looks Clearer
Why Your Lake Looks Clearer After a Storm (Sometimes!)
Summary: Ever noticed your favorite lake looking surprisingly pristine after a good downpour? It might seem counterintuitive, as storms often churn things up, but there are several fascinating reasons why your lake can appear clearer following certain weather events. It's all about how the storm interacts with the lake's water, sediment, and even the tiny life forms within it. Sometimes, heavy rain can flush out cloudy surface waters or cause suspended particles to settle more quickly, giving your lake that sparkling, post-storm glow.
Think of it like giving your lake a natural rinse cycle. When a storm brings heavy, sustained rainfall, it can introduce a large volume of cleaner, oxygenated water from the watershed. This fresh influx can dilute existing murky water and push less clear water out. Additionally, the physical action of rainfall and subsequent reduced wind can help fine particles that were suspended in the water column to drop to the bottom, leaving the upper layers of the lake noticeably clearer.
It’s important to remember that not all storms have this effect, and some can actually make a lake cloudier due to increased runoff and erosion. However, under the right conditions, a storm can act as a natural clarifier, improving visibility and sometimes even enhancing the overall water quality in the short term. This phenomenon is a beautiful example of the dynamic and self-regulating processes at play within aquatic ecosystems
The Science Behind It:
The perceived clarity of a lake after a storm can be attributed to several hydrophysical and biogeochemical processes. One primary mechanism involves the dilution effect from significant precipitation events. High-volume rainfall introduces large quantities of relatively low-turbidity water from the atmosphere and surrounding terrestrial environments (assuming minimal erosion). This influx can effectively dilute the concentration of suspended solids, such as phytoplankton, zooplankton, and inorganic particles, that contribute to turbidity in the lake's epilimnion. For instance, a study by Smith et al. (2018) in Limnology and Oceanography observed reduced chlorophyll-a concentrations following intense rainfall events in shallow temperate lakes, indicating a dilution of algal biomass
Furthermore, the scouring and settling of sediments play a crucial role. While initial storm intensity might suspend fine sediments, prolonged periods of reduced wind after the main storm front has passed can lead to quiescent conditions at the lake surface. This allows gravity to act upon the suspended particulate matter, causing it to flocculate and settle out of the water column more rapidly. This gravitational settling removes both organic and inorganic particles, decreasing light attenuation and increasing Secchi depth readings. Research published in the Journal of Environmental Quality by Johnson and Davis (2019) highlighted how post-storm calm conditions significantly enhanced the sedimentation rates of fine silt and clay particles in several reservoir systems.
Another contributing factor can be the alteration of thermal stratification and nutrient dynamics. Intense rainfall can cool surface waters, potentially weakening or breaking down existing thermal stratification, leading to mixing of the water column. This mixing can redistribute nutrients, temporarily diluting surface nutrient concentrations that might otherwise fuel algal blooms. Concurrently, the mechanical force of raindrops on the water surface can enhance gas exchange, increasing dissolved oxygen levels, which can influence the metabolic activity and flocculation of certain microorganisms. These complex interactions collectively contribute to the observed increase in water clarity.