Surface Water

 

Surface water is water in a river, lake or fresh water wetland. Surface water is naturally replenished by precipitation and naturally lost through discharge to the oceans, evaporation, and sub-surface seepage.

Although the only natural input to any surface water system is precipitation within its watershed, the total quantity of water in that system at any given time is also dependent on many other factors. These factors include storage capacity in lakes, wetlands and artificial reservoirs, the permeability of the soil beneath these storage bodies, the runoff characteristics of the land in the watershed, the timing of the precipitation and local evaporation rates. All of these factors also affect the proportions of water lost.

Human activities can have a large and sometimes devastating impact on these factors. Humans often increase storage capacity by constructing reservoirs and decrease it by draining wetlands. Humans often increase runoff quantities and velocities by paving areas and channelizing stream flow.

The total quantity of water available at any given time is an important consideration. Some human water users have an intermittent need for water. For example, many farms require large quantities of water in the spring, and no water at all in the winter. To supply such a farm with water, a surface water system may require a large storage capacity to collect water throughout the year and release it in a short period of time. Other users have a continuous need for water, such as a power plant that requires water for cooling. To supply such a power plant with water, a surface water system only needs enough storage capacity to fill in when the average stream flow is below the power plant's need.

Natural surface water can be augmented by importing surface water from another watershed through a canal or pipeline. It can also be artificially augmented from any of the other sources, however in practice the quantities are negligible. Humans can also cause surface water to be "lost" (i.e. become unusable) through pollution.

 

Tasks

 

1. Find in the text the sentence in which it is said that…

 

1). …вода на поверхности Земли естественным образом пополняется за счёт осадков.

2). …общее количество воды также зависит от многих других факторов.

3). …все эти факторы также влияют на пропорции потери воды.

4). …люди часто повышают количество потоков воды и их скорость путём мощения участков земли и направления этих потоков в русла.

5). …важно учитывать количество воды, доступной в данное время.

6). …другие пользователи, такие как электростанции, постоянно нуждаются в воде для охлаждения.

7). …люди, загрязняя воду, могут стать виновниками того, что вода будет «утеряна».