Water cycle

The water cycle, also known as the hydrologic cycle or H₂O cycle, describes the continuous movement of water on, above and below the surface of the Earth. Water can change states among liquid, vapor, and solid at various places in the water cycle. Although the balance of water on Earth remains fairly constant over time, individual water molecules can come and go, in and out of the atmosphere. The water moves from one reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by the physical processes of evaporation, condensation, precipitation, infiltration, runoff, and subsurface flow. In so doing, the water goes through different phases: liquid, solid, and gas.
The water cycle involves the exchange of heat energy, which leads to temperature changes. For instance, in the process of evaporation, water takes up energy from the surroundings and cools the environment. Conversely, in the process of condensation, water releases energy to its surroundings, warming the environment. The water cycle figures significantly in the maintenance of life and ecosystems on Earth. Even as water in each reservoir plays an important role, the water cycle brings added significance to the presence of water on our planet. By transferring water from one reservoir to another, the water cycle purifies water, replenishes the land with freshwater, and transports minerals to different parts of the globe. It is also involved in reshaping the geological features of the Earth, through such processes as erosion and sedimentation. In addition, as the water cycle also involves heat exchange, it exerts an influence on climate as well.

Precipitation

Condensed water vapor that falls to the Earth's surface . Most precipitation occurs as rain, but also includes snow, hail, fog drip, graupel, and sleet.^[1] Approximately 505,000 km³ (121,000 cu mi) of water falls as precipitation each year, 398,000 km³ (95,000 cu mi) of it over the oceans.^[2]

Canopy interception

The precipitation that is intercepted by plant foliage, eventually evaporates back to the atmosphere rather than falling to the ground.

Snowmelt

The runoff produced by melting snow.

Runoff

The variety of ways by which water moves across the land. This includes both surface runoff and channel runoff. As it flows, the water may seep into the ground, evaporate into the air, become stored in lakes or reservoirs, or be extracted for agricultural or other human uses.

Infiltration

The flow of water from the ground surface into the ground. Once infiltrated, the water becomes soil moisture or groundwater.^[3]

Subsurface flow

The flow of water underground, in the vadose zone and aquifers. Subsurface water may return to the surface (e.g. as a spring or by being pumped) or eventually seep into the oceans. Water returns to the land surface at lower elevation than where it infiltrated, under the force of gravity or gravity induced pressures. Groundwater tends to move slowly, and is replenished slowly, so it can remain in aquifers for thousands of years.

Evaporation

The transformation of water from liquid to gas phases as it moves from the ground or bodies of water into the overlying atmosphere.^[4] The source of energy for evaporation is primarily solar radiation. Evaporation often implicitly includes transpiration from plants, though together they are specifically referred to as evapotranspiration. Total annual evapotranspiration amounts to approximately 505,000 km³ (121,000 cu mi) of water, 434,000 km³ (104,000 cu mi) of which evaporates from the oceans.^[2]

Sublimation

The state change directly from solid water (snow or ice) to water vapor.^[5]

Advection

The movement of water — in solid, liquid, or vapor states — through the atmosphere. Without advection, water that evaporated over the oceans could not precipitate over land.^[6]

Condensation

The transformation of water vapor to liquid water droplets in the air, creating clouds and fog.^[7]

Transpiration

The release of water vapor from plants and soil into the air. Water vapor is a gas that cannot be seen.

Methods

Symptoms-based

Main article: Fertility awareness

Some methods of NFP track biological signs of fertility. When used outside of the Catholic concept of NFP, these methods are often referred to simply as fertility awareness-based methods rather than NFP.^[33] The three primary signs of a woman's fertility are her basal body temperature, her cervical mucus, and her cervical position.^[34] Computerized fertility monitors may track basal body temperatures, hormonal levels in urine, changes in electrical resistance of a woman's saliva or a mixture of these symptoms.^[35]
From these symptoms, a woman can learn to assess her fertility without use of a computerized device. Some systems use only cervical mucus to determine fertility. Two well-known mucus-only methods are the Billings ovulation method and the Creighton Model FertilityCare System. If two or more signs are tracked, the method is referred to as a symptothermal method. Two popular symptothermal systems are taught by the Couple to Couple League and the Fertility Awareness Method (FAM) taught by Toni Weschler.^[36] A study completed in Germany in 2007 found that the symptothermal method has a method effectiveness of 99.6%.^[37]
In Canada, the symptothermal method is taught by SERENA Canada which is an inter-denominational organization which has been developing the Symptothermal Method as a part of NFP since 1955. They are also not specifically affiliated with the Roman Catholic Church. It is also taught by Justisse Healthworks for Women, a pro-choice feminist organization that allows and supports women to combine other methods of birth control with their fertility awareness practice.

[edit] Calendar-based

Main article: Calendar-based methods

Calendar-based methods determine fertility based on a record of the length of previous menstrual cycles. They include the Rhythm Method and the Standard Days Method. The Standard Days method was developed and proven by the researchers at the Institute for Reproductive Health of Georgetown University. CycleBeads, unaffiliated with religious teachings, is a visual tool based on the Standard Days method. According to the Institute of Reproductive Health, when used as birth control, CB has a 95% effectiveness rating. iCycleBeads is the first iPhone app based on a natural family method, Standard Days. Women can plan or prevent pregnancy naturally via their iPhone or Apple brand device.^[38]

[edit] Lactational amenorrhea

Main article: Lactational amenorrhea method

The lactational amenorrhea method (LAM) is a method of avoiding pregnancy based on the natural postpartum infertility that occurs when a woman is amenorrheic and fully breastfeeding. The rules of the method help a woman identify and possibly lengthen her infertile period. A strict version of LAM is known as ecological breastfeeding.

Natural family planning (NFP) is a term referring to the family planning methods approved by the Roman Catholic Church. In accordance with the Church's requirements for sexual behavior in keeping with its philosophy of the dignity of the human person, NFP excludes the use of other methods of birth control.
Periodic abstinence and the natural infertility caused by breastfeeding are the only methods deemed moral by the Church for avoiding pregnancy. When used to avoid pregnancy, NFP limits sexual intercourse to naturally infertile periods; portions of the menstrual cycle, during pregnancy, and after menopause. Various methods may be used to identify whether a woman is likely to be fertile; this information may be used in attempts to either avoid or achieve pregnancy.

RH Bill

The Reproductive Health bills, popularly known as the RH Bill, are Philippine bills aiming to guarantee universal access to methods and information on birth control and maternal care. The bills have become the center of a contentious national debate. There are presently two bills with the same goals: House Bill No. 4244 or An Act Providing for a Comprehensive Policy on Responsible Parenthood, Reproductive Health, and Population and Development, and For Other Purposes introduced by Albay 1st district Representative Edcel Lagman, and Senate Bill No. 2378 or An Act Providing For a National Policy on Reproductive Health and Population and Development introduced by Senator Miriam Defensor Santiago.
While there is general agreement about its provisions on maternal and child health, there is great debate on its key proposal that the Philippine government and the private sector will fund and undertake widespread distribution of family planning devices such as condoms, birth control pills (BCPs) and IUDs, as the government continues to disseminate information on their use through all health care centers.
The bill is highly divisive, with experts, academics, religious institutions, and major political figures supporting and opposing it, often criticizing the government and each other in the process. Debates and rallies for and against the bill, with tens of thousand participating, have been happening all over the country.