BATANGAS STATE UNIVERSITY College of Engineering, Architecture, Fine Arts Gov. Pablo Borbon Campus II, Alangilan, Batangas City, Philippines 4200

www.batstate-u.edu.ph Telefax: (043) 300-4404 locs. 106-118

CHEMICAL AND FOOD ENGINEERING DEPARTMENT

Introduction

Water is a major factor in shaping our landscape. Through the processes of erosion and sediment transport, water forms many surface features such as valleys, flood plains, deltas, and beaches. Water also forms subsurface features such as caves. Natural wonders such as the Grand Canyon were, and are being, carved by water. Streams from upland areas carried much of the sand that is located on ocean beaches Water is a renewable resource. However, it is not always available when or where it needed, and it may not be of suitable quality for intended uses. Although we commonly take for granted that clean and abundant water is as close as the nearest faucet, water resourcesThe ocean is the source of most of the world’s precipitation (rainfall and snowfall), but people’s freshwater needs are met almost entirely by precipitation on land (see Figure 4.1), with a small though increasing amount by

desalination. Due to changes in the state of the ocean, precipitation patterns are altering, affecting human well-being. Ocean changes are also affecting marine living

resources and other socio-economic benefits on which many communities depend. The availability, use and management of freshwater, and of aquatic ecosystems in general, are key to development and human well-being.

The Water Cycle

The constant movement of water from oceans, to atmosphere, to land surface, and back to the oceans again is known as the water — or hydrologic — cycle. To understand water availability and quality, this cycle must be viewed at several spatial and temporal scales. Precipitation events that occur over a small area can cause local flooding, but have minimal effect on the larger watershed. Water can infiltrate rapidly into sandy soils, or run off rapidly from bare rock. Precipitation is the source of fresh water virtually everywhere on Earth, but the location, timing, and amount of precipitation are highly variable. Evaporation and transpiration return water to the atmosphere and also are highly variable in space and time. Water that falls to the Earth’s surface follows one of several paths, it evaporates, infiltrates into the soil, flows along the soil surface into streams or other water bodies, or recharges groundwater. Precipitation in the form of snow eventually (after melting) evaporates, infiltrates into the soil, flows into wate bodies, or recharges groundwater. While in its solid state, snow can lose water vapor to the atmosphere through sublimation. The portion of the precipitation that infiltrates into soils and is not captured by plant roots percolates into (recharges) the groundwater system. Because of large variations in the distribution of precipitation, evaporation, and transpiration, much of the water that falls on the Earth’s surface never reaches the ocean as stream or groundwater flow. As water moves through the hydrologic cycle, it comes in contact with natural and human-made materials that change its quality.

Water Cycle Spheres

Hydrosphere - Water moves from the earth to the atmosphere through the processes of evaporation and transpiration.

Evaporation is the transformation of water from its liquid form to its gaseous form as a result of coming in contact with heat or the air.

Transpiration is the process of plants releasing water through their leaves is called.

Atmosphere - Air that holds moisture until it falls as precipitation.

Precipitation is the moisture from the atmosphere that is returned to the earth in the form of snow or rain.

Biosphere - Includes all plant and animal life which are consumers of water.

Lithosphere - Land where water falls as precipitation.

Physical and Chemical Makeup of Water

Water, in its purest form, is tasteless, odorless, and colorless.

It is a chemical compound made up of two atoms of hydrogen and one atom of oxygen.

Its chemical symbol is H2O.

Solid form of water is called ice.

Water freezes at 32F or 0C.

Gaseous form of water is called water vapor or steam.

When water boils it turns into water vapor or steam. Water boils at 212°F or 100°C.

In between the gaseous and solid form, water is in its liquid form.

Water that contains salt is called saline water. Sodium chloride, potassium, and magnesium can raise the level of salts in the water. The amount of salt in the water will determine its usefulness. Water that is too high in salt cannot be used for drinking or irrigation.

Categories of Saline Water

Freshwater - Water with less than 3.0 parts per thousand (ppt) of salt. Most commonly found in drilled wells, streams, and lakes. Only 3 percent of the water on the earth is considered freshwater, of this 3 percent only 1 percent is available for use.

Saltwater - Water with 16.5 ppt or more of salt. Some ocean and sea water is as high as 33 to 37 ppt. Saltwater makes up about 97 percent of the earth’s water.

Brackish water - A mixture of saltwater and freshwater. Brackish water is found where freshwater flows into the ocean or other bodies of saltwater. An

estuary is the area where a freshwater stream flows into the ocean or a saltwater lake.

Flowing Bodies of Water

One of the most important parts of the water cycle is the stream.

Streams are flowing bodies of water that are useful resources for irrigation, factories, and local water systems.

Types of Streams

Stream type is determined by the volume and velocity of the movement of water, or streamflow.

The four types of streams are rivers, creeks, brooks, and canals.

Stream Hydrology

The study of flowing water and its environment.

The physical, chemical, and biological properties of the water and the surrounding environment are tested.

The ecosystems, including food webs, are studied.

Stream Structure

Determines how water moves within the stream and through the earth.

A stream is an important part of watershed or catchment.

The edge of a watershed is known as a drainage divide.

The area through which water flows in a stream is called a channel.

A channel is usually formed with rock or soil and it is the sides and bottom of the stream.

The bottom of the channel is called the stream bed, the sides are called the stream banks.

When a channel is not large enough to hold the flow of water the area that overflows is called a flood plain.

Non-Flowing Bodies

These bodies may be natural or artificial.

Non-flowing bodies of water influence the weather and climate of an area.

Commerce, food supply, and recreational activities can also be influenced by the non-flowing bodies of water in an area.

Bodies of water that do not flow still have water movement.

The internal movement is caused by temperature changes and salinity.

Types of Non-Flowing Bodies

Seven types of non-flowing bodies of water are:

Oceans - Large bodies of saltwater; Cover almost 75 percent of the surface of the earth.

Lakes - Bodies of freshwater that are surrounded by land; Vary in size, some are natural and others are man-made.

Ponds - Non-flowing bodies of water that are smaller than lakes; Commonly manmade and used as a source of recreation or for use by livestock.

Reservoirs - Large bodies of stored water; Commonly used to generate electric power.

Sloughs - Thick, muddy areas of shallow water. Marshes - Areas of land covered with shallow water and plants such as

cattails; Do not contain trees and are similar in nature to sloughs. Estuaries - Areas where freshwater streams flow into the ocean or a

saltwater lake; semienclosed coastal area, where seawater mixes with fresh water from rivers; also, the tidal area of the lower part of a river.

As in flowing streams, non-flowing bodies of water may contain a variety of ecosystems.

Pollution Sources

Point sources are direct discharges to a single point;

Examples include discharges from sewage treatment plants, injection wells,and some industrial sources.

Non-point sources are diffused across a broad area and their contamination cannot be traced to a single discharge point.

Examples include runoff of excess fertilizers, herbicides, and insecticides from agricultural lands and residential areas; oil, grease, and toxic chemicals from urban runoff and energy production; and sediment from improperly managed construction sites, crop and forest lands, and eroding stream banks.