Geography is a compulsory course for senior one, Unit 2, Section 2, Atmosphere, Weather and Climate, Third Water Saving Circle and Water Cycle.

I. Water cycle

(A) the concept and types of water cycle

1, water cycle

Refers to the spatial movement of water in the geographical environment (four circles), as well as the changes of its movement form and physical state.

2. Circulation between land and sea

There are many links in the water cycle, and the cycle process is complex and extensive. Such as landing typhoon and summer monsoon; Flowing out of rivers into the sea and so on are all system types.

3. Inland circulation

There are few water circulation links, such as the melting of snow and ice in mountainous areas and the water circulation in inland rivers and lakes.

4. Ocean internal circulation

The amount of water vapor is large and there are few links, and most of the water vapor evaporated from the ocean falls back to the ocean.

(b) Energy sources and significance of water cycle

1. The energy of water cycle comes from solar radiation energy and gravity energy.

The process of water cycle is a large-scale transfer of energy in geographical environment.

2. The significance of water cycle

Contact the four circles to maintain the dynamic balance of global water and make the land water constantly updated; Realize material migration and energy exchange between circles and between land and sea; Affect the global climate and ecology; Constantly shape the surface morphology.

(c) Water cycle and water resources

1, water resources are renewable resources.

Water is a renewable resource. Generally speaking, areas with more precipitation and active water circulation are rich in water resources.

2. Water resources are not inexhaustible.

Generally speaking, the water cycle is governed by natural laws. In a certain time and space, the regenerative capacity of water cycle is limited. If humans overuse water resources, water resources will also be exhausted.

3. The spatial and temporal distribution of water resources is uneven.

The uncoordinated distribution of population, land and water resources, man-made pollution and destruction of water resources have aggravated the shortage of water resources.

The source is tight.

(d) The impact of human activities on the water cycle

1. Human activities have the greatest influence on surface runoff and surface evaporation.

Reasonable impacts: diversion irrigation, inter-basin water transfer, reservoir construction, planting trees and grass, etc.

Unreasonable effects: large-scale deforestation, draining swamps, reclaiming land from lakes, over-exploitation of groundwater and hardening.

Wait.

2. Artificial precipitation enhancement

Local implementation. Small scale, only when the weather is suitable can it be successful, and it has little influence on the distribution of precipitation in a large range.

Second, the supply of rivers.

(A) the main types of river recharge

1, rainwater supply

Generally, the change of river flow is consistent with the change of precipitation, and the rainy season forms the flood season. The runoff of many rivers has obvious seasonal and interannual changes.

Examples show that the seasonal variation of runoff in some rivers is not obvious.

2. Seasonal snowmelt water supply

Forming spring floods, such as rivers in Northeast China.

3. Permanent snowmelt water supply

Recharge is related to temperature, and the recharge amount is small, which forms a flood season in summer and often stops in winter.

4. Lake water supply

Lakes in the middle and lower reaches of rivers mainly have the function of peak clipping and drought compensation, and large reservoirs also have this function; Lakes in mountainous areas can be the source of rivers.

5. Groundwater recharge

The supply is small and there is no obvious seasonal change. The two are complementary.

(B) the impact of human activities on the hydrological characteristics of rivers

Human activities can change the water quantity and sediment concentration of rivers.

1, destroy vegetation, plant trees and grass.

Surface runoff increases (decreases), the river water level rises and falls sharply (slowly), and the high (low) peak water level comes early (late); River sediment concentration increases (decreases).

During the flood period, sediment deposition, river bed uplift, high water level and large amount of water.

2. Build reservoirs and reclaim land around lakes.

Make the river water quantity change smoothly (the water level rises and falls obviously), and reduce the sediment concentration in the downstream river (aggravate the downstream flood disaster).

3. Harden the urban pavement and lay water-permeable bricks.

Increasing (decreasing) surface runoff is not conducive to (beneficial to) surface water infiltration, and the river water level rises and falls sharply (slowly), causing urban floods or water shortages and aggravating (alleviating) urban water resources problems.

Second, ocean currents.

(a) Formation and classification of ocean currents

1. Ocean current is one of the main forms of seawater movement.

2. The formation of ocean current is influenced by many factors.

Atmospheric movement and main wind direction; Geostrophic deflection, land shape, etc.

3. Ocean current classification

(1) Warm current and cold current

(2) According to the causes, it can be divided into wind current, density current and compensation current.

There are many wind currents, such as trade winds, west wind drift, seasonal winds and circumpolar circulation; Compensation current (upwelling) is obvious on the east coast of the ocean; There are density currents between oceans with different salinities and densities.

(b) Distribution of ocean currents

1. In tropical and subtropical waters, an ocean circulation centered on the subtropical zone is formed.

The circulation in the northern hemisphere is clockwise and that in the southern hemisphere is counterclockwise. The west coast of the ocean is warm,

The east coast is very cold.

2. At the mid-high latitudes in the northern hemisphere, an ocean circulation centered on the sub-polar region is formed. The circulation in the northern hemisphere is clockwise, the circulation in the southern hemisphere is counterclockwise, the western ocean is cold current (wind current) and the eastern ocean is warm current.

3. In the sea area of about 40 S, the global west wind drift is formed, and the circumpolar circulation (counterclockwise) is formed near the South Pole.

4. In the northern Indian Ocean, due to the formation of monsoon, the direction of ocean current changes seasonally.

In winter, the northeast wind prevails, and the seawater flows to the west or southwest, forming a counterclockwise circulation; Popular in summer

Southwest monsoon, seawater flows to the east or northeast, forming clockwise circulation (Somali cold current appears, is

Strong upwelling).

(c) the impact of ocean currents on the geographical environment

1, the impact on climate

(1) transfers and exchanges heat between high and low latitudes, and regulates the global heat distribution.

(2) Impact on climate in coastal areas

Sea fog is easy to form at the junction of cold current and warm current and the area where cold current flows, which affects the maritime traffic.

Warm current can make coastal areas warm and humid (the average temperature in Leng Yue on the east coast of the North Atlantic warm current is higher than that on the west coast of the ocean 16-20℃). For example, the temperate maritime climate in western Europe is widely distributed, and the temperate deciduous broad-leaved forest extends northward to 60° N；; ; Murmansk port is not frozen in winter, which is closely related to the North Atlantic warm current. Formation of tropical rain forest climate in four special areas.

The cold current can reduce the temperature and humidity in the coastal areas of the mainland, such as the formation of the subtropical west coast desert; East Asia

The latitude of coniferous forest in sub-cold zone is lower than that in western Europe (50° N-70° N). West wind drift's "Wind"

The "wall effect" and its own cold current nature aggravated the cold of Antarctic continent.

2. Impact on the distribution of marine life

At the intersection of cold current and warm current, fish are rich in food and bait, forming a famous fishing ground, such as Hokkaido fishing ground.

North Sea Fishing Ground, Newfoundland Fishing Ground. There is upwelling along the coast of Peru, forming a fishing ground in Peru.

3. Impact on marine pollution

Ocean current is beneficial to the diffusion of pollutants and accelerates the purification speed; With the movement of ocean currents, the pollution scope expands.

4. Impact on navigation.

Smooth sailing saves time and fuel; Sailing against the wind and current is slow, wasting time and energy. many

Sea fog area is not conducive to maritime navigation; Ocean currents carry icebergs from the Arctic to the south, which is a safe zone for ships.

To threaten.

194 1 65438+On February 7th, Japan attacked Pearl Harbor in the United States, and its aircraft carrier approached Pearl Harbor along the westerlies.

There is no trade wind, try to analyze the reasons.

Take the westerly route: short voyage, calm and foggy sky, which is conducive to concealment; The westerlies are very stormy.

High, poor security.

Take the trade wind route: small wind and waves, good safety; For Japan, the voyage is long, the wind is against the current and the speed is slow.

Easily detected by the United States.