Many things happen during the winter that disrupt the equilibrium of water bodies, like increased debris from trees and activity from migrating and native waterfowl. Some things take place that you can't see, such as rainfall increases during the winter. Rainfall contains a surprising amount of nitrogen picked up from the atmosphere. Runoff caused by rainfall also moves fertilizers and debris from the watershed into the lake. Rainfall can also change the chemical balance (pH).

Spring renovation will bring the body of water back to equilibrium before high summer temperatures and sunlight favor aquatic weeds and algae. The goal is to reduce organic matter suspended in the water, adjust the pH of water to be favorable to chemical breakdown, and to improve the oxygen content. Other steps can be taken to improve lake health and discourage weeds, such as increasing lake depth and circulation, using dyes to reduce sunlight penetration, and preventing runoff and debris from reaching the water in the lake. Reducing organic matter involves filtration or treating the water to cause organic particles to settle to the bottom. Filters are mechanical devices that require pumps, piping, a filter media, and power. The filter media must be flushed or replaced regularly to be effective. The time between filter maintenance events is determined by the load of suspended material in the water and the volume of water passing through the filter.

Treating a lake with chemicals requires sufficient circulation and an accurate calculation of the volume of water in the lake. The product needs to be both effective and safe for fish and irrigation, if the lake is used as a reservoir. It must be applied correctly and evenly distributed throughout the body of water. Clarification treatment should be followed with other steps to reduce light penetration and increase oxygen circulation. And, of course, now is the time to get serious about preventing debris from trees and lawns from entering the body of water.

The acidity or alkalinity of a lake influences how rapidly organisms function to digest contaminants. These organisms perform best at a certain range of pH, which represents the amount of hydrogen present in the water. A balanced pH is 7.0. Tree leaves and rain are acidic. Likewise, a lake with a limestone shoreline can become too alkaline. The lake pH can change over time and reduce the effectiveness of beneficial organisms. The lake can be treated to restore pH. Depending upon the size and depth of your water feature, some provision should be made to maintain circulation throughout the year.

A lake should be designed to be deep enough so that sun does not encourage establishment and growth of bottomrooted weeds. Seed for those aquatic weeds can enter a lake from birds or simply by the wind. Lake dyes can be used to prevent the sun from reaching the lake bottom and to impart a bluer cast to your lake. Deep lakes can develop layers of water at different temperatures. This is called stratification. The temperature of each layer determines how much oxygen it will hold, with cooler water holding more oxygen. By causing water in the lake to circulate, the layers are mixed and the oxygen level is consistent throughout the entire body of water. Water that doesn't circulate will also tend to hold more suspended material. This leads to discoloration and odors. Circulation causes suspended material to fall to the bottom of the lake, where bacteria can break it down. Certain treatments can also cause suspended material to drop out.

Floating, motorized pumps can be installed in lakes to either pump air into the water (injector) or to pump the water into the air. While these will provide additional oxygen to a lake, they also increase the temperature of the lake to be more like the air above it. The air pumped into a lake will not be evenly distributed throughout the lake without proper circulation. An injector that uses a pump on the lake shore can also inject oxygen into the lake through tubes stretched across the lake bottom. All these devices take energy to run and require maintenance to operate properly.