Water is an important resource and in many countries, waterways are increasingly clogged by aquatic plant growth. This is particularly so in tropical countries where warmer water means the plants grow more quickly, and increasing run-off of fertilizer and effluent has exacerbated the problem. Irrigation ditches and pumps can become overgrown with vegetation, power station and factory water intakes can get blocked, boats can get hindered, fish stocks can be disrupted, and water moves more slowly, resulting in greater evaporation and a greater risk of flooding. In some large irrigation projects in India, canals have become so overgrown with vegetation that water flow has been reduced to a fifth of its previous amount
Water chestnut forms dense mats that shade out native aquatic vegetation, leading to a decrease in biodiversity. Decomposition of vegetation below a dense mat decreases oxygen levels and can cause fish kills. Boating and other recreational activities become almost impossible in an area invaded by water chestnut.
