The most important aspect is in industry where aquatic plants get to be a problem in the intakes into power plants and factories. Another big problem area is in agriculture, especially irrigation. The plants plug up irrigation ditches causing uneven water flow, etc (this has been a big problem in AZ in the past 50 years). The third big area is in recreation such as fishing, boating, swimming, and sailing. There is a lot of money spent on weed control in these areas. Part of the problem with control is that you are going against the natural aging process of the lake.

Reverse natural processes: 1) aging process, 2) excess nutrients from erosion and pollution

Look At The Problem
1) Determine the water use: Why do you want to control this water? For what purpose? It is often not necessary to have total elimination.
2) Safety of the method(s) going to be used: -safety of the applicator, water users, and the environment
3) How effective and for how long is this control method?
     A) % removal
     B) Time to do the work (application itself and the time it takes to become effective)
     C) Longevity
     D) Cost-benefit analysis
     E) Side Effects: What other impacts will you have on wildlife, the environment, and people? Erosion and water storage capacity (control usually affects these two things greatly).

Link to Biological and Chemical Methods

Physical Methods
1) Removal - by hand, rakes, cutting, digging
-lots of equipment to do this with ( special shovels, chains, hooks, etc)
-good for a small area, but it is hard work
-problems with rhizomes, tubers and seeds left behind
-if you pay someone to do it, it can get expensive

2) Mechanical - underwater mowers, backhoes, dredges (like for shipping channels)
-even more expensive but can do bigger areas
-problem with this: backhoes and dredges tear up the substrate destroying benthic communities and can also release even more nutrients and pollutants that were buried in the soil.
-creates negative wildlife impacts: negative effects on benthic fauna, disrupts spawning
- disposal problem with wet material (maybe used for animal feed, mulch, soil conditioner)

3) Habitat Modification
a) Line or cover the bottom when pond or lake is new, especially if it is a constructed wetland or reservoir. Maybe expensive at first, but over the long run, the cheapest. Can be made with plastic, concrete, or soilcrete, or by dumping sand or gravel on the bottom to cover up the plants.
b) Shading - (often done on smaller bodies of water) plastic sheets or floating covers. People have tried plastic film canisters, soluble dyes, overhanging trees, and swimming rafts
c) Draw down or drying period- dry out shallow areas and kill the plants there. This is done in irrigation systems, farm ponds, recreational lakes, etc.
d) Flood or fill up the water body - kills emergent plants
e) Flushing - knocks loose plants, blast water through. Works well in irrigation ditches.
f) Dredging (from shore or boat) - has a lot of negative impacts. What do you do with the stuff you dredge up?
g) Fertilize water - algae bloom will compete with other aquatic plants, plants will die, and then the algae will die off
h) Weed net screens

4) Management (mostly Watershed Management)
a) don't fertilize slopes of the water body, grassy yards, golf courses
b) maintain septic tanks, reduce nutrient flows
c) prevent dumping or blowing of fireplace ashes, leaves, grass clippings, and other organic matter
d) planting buffer strips - one of the very best things you can do, traps nutrients, shades surface
e) rock lining edges (rip rap) - organic matter gets trapped here instead of going out to the water, reduces runoff and erosion
f) fencing out livestock - keeping waste out as well as animals
g) stop overfeeding fish