Fresh water

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**1. Freshwater Sources and Distribution:**
– Fresh water contains low concentrations of dissolved salts and total dissolved solids.
– Encompasses ice, snow, rainfall, surface runoffs, wetlands, ponds, lakes, rivers, streams, and groundwater.
– Less than 3% of the world’s water resources is fresh water, with just 1% readily available.
– Agriculture uses about two thirds of all extracted fresh water.
– Fresh water has less than 500 parts per million (ppm) of dissolved salts.
– Precipitation from mist, rain, and snow is the primary source of fresh water.
– Saline water makes up about 97% of Earth’s water, with fresh water comprising only 2.5-2.75%.
– Of the fresh water, 1.75-2% is frozen in glaciers, ice, and snow, and 0.5-0.75% is fresh groundwater.
– Freshwater lakes hold 87% of fresh surface water.

**2. Freshwater Ecosystems:**
– Subset of Earth’s aquatic ecosystems.
– Include lakes, rivers, springs, wetlands.
– Can be lentic, lotic, or wetlands.
– Contain 41% of known fish species.
– Underwent transformations over time.

**3. Water Scarcity and Pollution:**
– Increase in world population strains water resources.
– Freshwater ecosystems respond to climate change in terms of quality, quantity, timing.
– Water scarcity includes physical and economic scarcity.
– Drivers of global water demand include population growth, changing diets.
– Scarcity caused by mismatch in water availability and demand.
– Water Pollution: Contamination of water bodies from human activities.
– Sources include sewage discharges, industrial and agricultural activities, urban runoff.
– Pollution can lead to degradation of aquatic ecosystems and water-borne diseases.
– Drivers of water scarcity include climate change, pollution, and deforestation.

**4. Water Management and Conservation Goals:**
– Sustainable Development Goals consist of 17 global goals for a sustainable future.
– SDG 6 and SDG 15 include targets for fresh water conservation.
– Target 6.4 aims to increase water-use efficiency and reduce water scarcity by 2030.
– Target 15.1 focuses on conserving terrestrial and freshwater ecosystems by 2020.
– Integrated water resource management is essential for sustainable development.

**5. Water Treatment and Impact:**
– Wastewater treatment involves physical, chemical, and biological processes.
– Primary treatment removes solid waste from wastewater.
– Secondary treatment uses bacteria to break down organic matter.
– Tertiary treatment further purifies water to meet quality standards.
– Advanced treatment technologies like membrane filtration are becoming more common.
– Water pollution harms aquatic ecosystems and biodiversity.
– Contaminated water poses health risks to humans and wildlife.
– Nutrient pollution leads to harmful algal blooms.
– Polluted water affects fisheries and agriculture.
– Addressing water pollution requires collaborative efforts from governments, industries, and communities.

Fresh water (Wikipedia)

Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include non-salty mineral-rich waters such as chalybeate springs. Fresh water may encompass frozen and meltwater in ice sheets, ice caps, glaciers, snowfields and icebergs, natural precipitations such as rainfall, snowfall, hail/sleet and graupel, and surface runoffs that form inland bodies of water such as wetlands, ponds, lakes, rivers, streams, as well as groundwater contained in aquifers, subterranean rivers and lakes. Fresh water is the water resource that is of the most and immediate use to humans.

Amazon River near Iquitos, Peru
Lake Baikal as viewed from the Olkhon Island
Aerial view of Everglades with sawgrass and coastal marsh
Rivers, lakes, and marshlands, such as (from top) South America's Amazon River, Russia's Lake Baikal, and the Everglades in Florida of The United States, are types of freshwater systems.

Water is critical to the survival of all living organisms. Many organisms can thrive on salt water, but the great majority of vascular plants and most insects, amphibians, reptiles, mammals and birds need fresh water to survive.

Fresh water is not always potable water, that is, water safe to drink by humans. Much of the earth's fresh water (on the surface and groundwater) is to a substantial degree unsuitable for human consumption without some treatment. Fresh water can easily become polluted by human activities or due to naturally occurring processes, such as erosion. Fresh water makes up less than 3% of the world's water resources, and just 1% of that is readily available. Just 3% of it is extracted for human consumption. Agriculture uses roughly two thirds of all fresh water extracted from the environment.

Fresh water is a renewable and variable, but finite natural resource. Fresh water is replenished through the process of the natural water cycle, in which water from seas, lakes, forests, land, rivers and reservoirs evaporates, forms clouds, and returns inland as precipitation. Locally, however, if more fresh water is consumed through human activities than is naturally restored, this may result in reduced fresh water availability (or water scarcity) from surface and underground sources and can cause serious damage to surrounding and associated environments. Water pollution also reduces the availability of fresh water. Where available water resources are scarce, humans have developed technologies like desalination and wastewater recycling to stretch the available supply further. However, given the high cost (both capital and running costs) and - especially for desalination - energy requirements, those remain mostly niche applications. A non-sustainable alternative is using so-called "fossil water" from underground aquifers. As some of those aquifers formed hundreds of thousands or even millions of years ago when local climates were wetter (e.g. from one of the Green Sahara periods) and are not appreciably replenished under current climatic conditions - at least compared to drawdown, these aquifers form essentially non-renewable resources comparable to peat or lignite, which are also continuously formed in the current era but orders of magnitude slower than they are mined.

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