Freshwater Systems – Rivers and Streams

Planet Earth should be called Blue Planet or Planet Water. The reason is obvious. Just look at it!

Among all water in the planet drinkable water is rare. Since 97.5% of the water is found in the ocean and is too salty to drink or use to water crops, which leaves us with only 2.5% of fresh water, with few dissolved salts. Yes, there is desalination technology to remove salt from sea water and have fresh water. This process is used by many countries and cities but it is really expensive. I can talk more about it on another post.

Since most fresh water is tied up in glaciers, icecaps and underground aquifers, just over 1 part in 10,000 of Earth’s water is easily accessible for human use.

Glacier - forms in locations where the mass accumulation of snow and ice exceeds ablation over years. As they move and flow they shape the landscape

Ice caps - bodies of ice located at the earth's poles. More stagnant than glaciers, it's land area is less than 50 000 km². Land areas with more than 50 000 km² are ice sheets

Water constantly moves among the reservoirs via the hydrologic cycle. As it does so it distributes heat, erodes mountain ranges, builds river deltas, maintains organisms and ecosystems, shapes civilizations, and also gives rise to political conflicts.

As water physically shapes Earth’s landscapes, fresh water systems support a large fraction of our planet’s organisms. Several freshwater ecosystem types can be thought of as the aquatic equivalents of biomes.

On this post I will start talking about these freshwater systems. Despite the fact that they are not that many, there is a lot to talk about each of them, so I’ll talk about them one post at a time.

The freshwater systems are:

• Glaciers;
• Lakes and ponds;
• Rivers and streams and
• Underground aquifers

As a whole, you’ll find in the next few posts things like:

• The importance of freshwater systems to us, human beings;
• The importance of freshwater systems to ecosystems that depend on them;
• How freshwater systems relate to the ecosystem as a whole. For instance, why cutting the trees on water bodies margins cause erosion, sedimentation, droughts and floodings among many other problems;
• How freshwater systems affect one another, since they are connected.
• What actions we take that can affect these freshwater systems and the ecosystems related to them;
• How our actions affect freshwater systems and the ecosystems related to them;
• The consequences of anthropogenic actions and what can be done to prevent them.

Freshwater ecosystems – Rivers and Streams

Rivers and streams are formed by water from rain, snowmelt, or springs that run downhill and converge where the land dips lowest, forming streams, creeks, or brooks. Such water courses merge into rivers which, eventually, reach the ocean or a landlocked water body.

The landscape is shaped by the rivers and areas flooded by rivers periodically are said to be within the river’s floodplain.

Agriculture thrives in floodplains because its soil is fertile due to the deposition of silt from floodings.

Waters of rivers and streams host diverse ecological communities and riparian (riverside) forests, that are productive and species-rich.

Like any other ecosystem, the rivers and riparian forests depend on each other to survive. Without the river and stream the soil isn’t fertile enough for the riverside forest to exist.

The riverside forest, on its turn, is important to the river because:

1. Riparian forests maintain the high water quality needed for supplying drinking water and maintaining diverse forms of aquatic life.

Nitrogen and phosphorus are found naturally in the environment and are necessary for aquatic plants and algae to grow and reproduce. However, excess nitrogen and phosphorus can be very damaging to the aquatic environment.

Because of human activities phosphorus and nitrogen are also found in fertilizers, septic leachate, sewage treatment plants, urban runoff, detergents, road dust, grass clippings, and yard debris.

When such nutrients are found in excess they can cause the rapid growth of algae and aquatic plants, which can reduce the amount of light penetrating the water and provoke death to aquatic plants and fishes. This process is called eutrophication.

When this algae dies, it’s decomposed by bacteria that use oxygen, lowering the amount of oxygen in the water. The depletion of oxygen causes taste and odor problems in drinking water and can also cause fish and other aquatic organisms to die or move.

Organisms that thrive in low oxygen environments release hydrogen sulfate and methane, chemicals that can be toxic to aquatic life and can compound the problem of an oxygen-deprived environment.

2. Riparian forests act as nutrient filters, sinks and transformers to help reduce the amount of nutrients reaching streams. Since most phosphorous is bound to small soil particles and both are filtered down, the remaining that is not soil bound is not removed by filtration, but by other mechanisms:

Riparian forests function as a nutrient sink. They sequester nitrogen and phosphorus in biomass and improve the ability of soils to hold nutrients by adding organic material to the soil. As water flows over the surface or as groundwater moves within the root zone of riparian plants, the plants actively uptake nutrients and absorb them. This plant material is removed from the riparian forest when it’s eaten or incorporated into animal biomass.

Studies have shown that riparian forests can remove a lot of nitrate (a form of nitrogen) and

phosphorus from agricultural runoff. The storage of these nutrients in the riparian forests reduces the amount of nutrients reaching streams and lakes. I would like to give you an idea in numbers for the amount of nutrients removed by the riparian forests, but these numbers seem to vary from area to area, influenced by the type of soil, climate, types of flora and other characteristics.

Here is a study from Iowa State University; and here an article about the importance of riparian forests that are examples of these studies for the amount of nutrients removed by the forests.

Riparian forests act as nutrient transformers as they change the chemical composition of nutrient compounds. When soil moisture is high enough to create anaerobic conditions in surface soil layers, bacteria can convert dissolved nitrate do gaseous nitrogen, releasing it safely into the atmosphere and reducing the amount reaching streams.

Here you can find a an interactive animation of the nitrogen cycle that I find it really interesting!

They are also capable of transforming toxic chemical and pesticides to nontoxic forms through microbiological decomposition, oxidation, reduction, hydrolysis, and solar oxidation.

3. The conservation of riparian forest is important in stabilizing stream banks, reducing erosion, and providing high quality wildlife habitat.

Stream banks are stabilized by the riparian forests deep root systems, which hold the soil in place and provide a degree of roughness capable of slowing runoff velocities and spreading flow during storms.

Riparian forests help prevent erosion of stream banks and the production of sediments. Without forest buffers, stream flow scours the streambed and banks leading to bank erosion and channel straightening. Straight channels lead to accelerated stream flow velocity and additional stream bank erosion, leading to the development of wide shallow streams with elevated temperatures and a low diversity of aquatic species.

4. Riparian forest helps on the maintenance of proper stream temperature and a healthy ecosystem.

Rriparian forest forms a canopy, that shades the stream. The shade moderates water temperature and protects it against fluctuations in temperature that can be detrimental to the stream ecosystem’s health.

Elevated temperatures reduce the amount of dissolved oxygen in the water and reduce fish spawning and survival. Studies have shown that, for example, when stream surface shade is reduced to 35%, trout population drop as much as 85%.

The amount of light reaching the stream also affect the types of algae produced in the stream. The type of algae growing in wooded areas are different from the ones in the open sunny areas. Fish eat macroinvertebrates and they prefer to eat the algae growing in wooden areas –diatoms- to the ones in sunny areas –filamentous green-. Because of that, the amount of sun defines the amount of each type of algae to grow and the types of food available for fish and other aquatic organisms.

What happens when there is a nutrient excess in a water body..

Macroinvertebrates, small animals eaten by fish

Diatoms, algae eaten by macroinvertebrates. Grow in wooded areas

5. The stream riparian forest function as source of food and energy for different forms of life and also provides diverse and high quality wildlife habitat.

The many kinds of plants like grasses, shrubs, vines and trees grow in the riparian forests providing important habitats because they make available nesting areas for birds and other animals as well as a variety of food items for wildlife.

The unbroken riparian forest also provides a pathway called ecological or wildlife corridor, important for the movement and migration of animals. It works as a connection between isolated blocks of forests, important to keep a high bio and genetic diversity. Here is an interesting short article about wildlife corridors from the science and nature writer DeLene Beeland. Here is a 4 page article about wildlife corridors design.

Even the woody debris that falls into the stream has its’ importance since it provides cover for fish and invertebrates. The debris forms debris dams that form pools providing space, cover, protection from high flow and a diversity of microenvironments for fish and other aquatic life.

Debris dams also block the transport of sediment and smaller litter materials. Such delay in transport of organic material down stream allows sufficient time for aquatic organisms to utilize it. The slowing of transport helps protect the sudden deposition of sediments down stream. There are studies that have shown a link between the presence of large woody debris and habitat quality, population growth of fish, and a diversity of fish and other aquatic organisms. Since fish also have non-aquatic predators, their presence attracts other animals, again increasing the biodiversity.

Example of a woody debris dam

The woody debris, stems, leaves, buds, flowers, etc., that fall into the stream from riparian forest form the basis of the aquatic food chain. This organic material is broken down into small pieces by aquatic insect larvae, crayfish and other invertebrates; bacteria and fungi breaks these small pieces into very fine material known as detritus, used for food by many small aquatic animals that are food for bigger aquatic animals. It’s a very delicate balanced environment, everything is interconnected. If something happens on one end everything else is affected as well.

6. Riparian forest is important in stabilizing stream banks, reducing erosion, and providing high quality wildlife habitat.

As water passes through a riparian area, the roughness of the forest floor and the vegetation help reduce the energy of the water flow allowing some of the water to infiltrate into the ground to be stored in wetlands and reduce downstream flooding, reaching groundwater, and maintaining stream base flow during the summer months.

Storm water treatment options that integrate natural systems and bioretention areas, such as riparian forests, are less expensive to construct than storm drain systems and provide better environmental results. Here is a website that almost teaches you to make a bioretention system.

Riparian forests can save money by providing protection from floods and management of storm waters. Storm water treatment options that integrate natural systems and bio-retention areas, like riparian forests, are less expensive to construct than storm drain systems

* In the flood of 1993 in the Midwest, the forested floodplain areas had less damage to the levee system and river than grass or farmland areas. A savings of $50,000 to $250,000 per mile in property damage was calculated. Here you can learn more about the effects of the Midwest Flood on wetlands.

7. Riparian forests function as efficient sediment filtering systems that are environmentally sound and economically advantageous.

Sediment is carried to streams from sources such as cropland erosion, pasture erosion, range erosion, road and construction sites, and stream bank deterioration.

The problem is that sediment suspended in water can reduce the penetration of sunlight into the stream and affect the growth of aquatic plants;

Since sediment can make the water cloudy, aquatic organisms may have some difficulty to find food and fish can have their gills clogged or damaged;

When sediment gets deposited on the stream bottom it affects the bottom dwelling fish and insects and it also destroy fish spawning areas.

Large sediment deposits can fill in stream channels and increase the potential for flooding

Help reduce the amount of sediment reaching streams because sediment settles out when the speed of water flow is reduced as it enters the riparian forest due to contact with vegetation, decaying leaves, twigs, and branches. In addition to that, sediment is removed as water runoff and sediment infiltrate into and are incorporated into the porous forest floor. Mature riparian forests can reduce the sediment load of water flowing from upland crop fields by eighty percent.

Marine and Coastal Systems

An adequate and clean supply of fresh water is vital to our survival and to Earth’s ecosystems, but recall that fresh water makes up only 2,5% of our planet’s water. Fully 97,5% is salt water, comprising the oceans that cover 71% of our planet’s surface. The oceans influence global climate, teem with biodiversity, facilitate transportation and commerce, and provide us many resources.

The world’s five major oceans – Pacific, Atlantic, Indian, Artic, and Antartic – are all connected, comprising a single vast body of water. Ocean water is salty primarily becase rivers and winds carry sediments and sals from the continents into the ocean. Evaporation then removes pure water, leaving a higher concentration of salts. If we were able to evporate all the water from the ocean, the world’s ocean basins would be covered with a layer of dried salt 63m (207 ft) thick.

Surface waters of the oceans are warmer than subsurface waters because the sun heat them and because warmer water is less dense. Deepbelow the surface, water is dense and sluggish, unaffected by winds and storms, sunlight, and daily temperature fluctuations. Ocen water moves in currents, vast riverlike flows that move in the upper 400m of water, horizontally and for great distances. Wind, solar heating and coling, gravity, density differences, and the Coriolis effect drive the global system of ocean currents. hese lon lasting patterns influence global climate, El Niño andLa Niña events, and navigation and human history.

Marine and coastal ecosystems are diverse. Their variation in topography, temperature, salinity, nutriens, and sunlight, marine and coastal environments feature  variety ofecosystems:

• Near-surface pelagic ecosystem – areas oft he open ocean where the photosynthetic productivity is concentrated near the suface in regions o nutrient-rich upwelling. Phytoplankton constitute the base of the marine food chain. Pedators at higher trophic levels include larger fish, sea turtles, shraks, and seabirds.

• Deep ocean – little-known, the deep ocean’s animals have adapted to deal with extreme water pressures and to live in th dark without food from photosynthesizers. Some of these bizarre-looking creatures scavenge carcasses or detritus that fall from above.

 

• Kelp forets - large brown algae, or kelp, grow from the floor of continental shelves, reaching toward the sunlit surface for up to 60m  (200 ft) in height.  Dense stands of kelp form underwater forests in many temperate waters. Kelp forests supply shelter an food for invertebrates and fish, which in turn provide food for predators such as seals, sharks, and seaotters. Kelp forests also absorb wave energy and protect shorelines from erosion. People derive alginates from kelp, which serve as thickeners in a wide range of consumer prducts, from cosmetics to foods to pains to paper to soaps.

• Coral reefs - is an underwater outcrop of calcium carbonate composed of the skeletons o tiny marine aimals known as corals. Corals attach to rock of existing reef nd capture passing food with stinging tentacles. They also derive nouishment from symbiotic algae, known as zooxanthellae, that inhabit their bodies and produce food through photosynthesis. Most corals are colonial, and the colorful surface of  coral reef consists of thousands of millions of densely packed individuals. As corals die, their skeletons remain part o the reef while new corals grow atop them, increasing the reef’s size. They absorb wave energy, protect shorelines, and host as much biodiversity as any other type of ecosysem. The likely rason is that coral reefs provide complex physical structure in shallow nearshore waters, which are regions of high primary productivity. Besides the staggering diversity of anemones, sponges, hydroids, tubeworms, and other sessile invertebrates, innumerable molluscs, crustaceans, flatworms, seastars, and urchins patrol the reefs, and thousans of fish species fnd food and shelter in reefnooks and crannies. Larger predators, such as grouper and mora eels, feed on the smaller fish.

• Intertidal zones – where he ocean meets the land, intertidal, or littoral, eosystems extend between the farthest reaches of the high and low tides, which are the periodic rising and falling of the ocean’s heigh at a given location, caused  by the graviational pullof the moon and sun. Intertidal organisms spend part of each day submerged in water, part of the day exposed to the air and sun, and part of the day being lashed by waves. Sessile nimals such as anemones, mussels, and barnacles live attached t rocks, filter-feeding on plankton in the water that washes over them.

• 

 

 

 

 

 

 

• Salt marshes – along many of the world’s coaslines at temperate latitudes, salt marshes occur where the tides wash over gently sloping sandy or silty substrates. Rising and falling tides fow into and out of channels, and at highest tide, water spills over onto elevated marsh flats. Marsh flats grow thick with rushes, shrubs, and grasses. Salt marshes boast very high primary poductivity and provide critical habitat for shorebirds, waterfowl, and the adults and young of many commercially important fish and shellfih species.

• Mangroe forests – in tropical and subtropical latitudes, mangroveforests occur along sandy and silty coasts. Mangroves are trees with odd rots, some of which curve upward like snorkels to attain oxygen lacking in the mud, and some of which curve downward, serving as silts to support the tree in changing water levels. Fish, shelfish, crabs, snakes, and other organisms thrive amont the root network, and bird feed and nest in the foliage of these coastal forests. Mangroves protect coastlines; studies fter the 2004 South Asian tsunami indicated that coasts wth intact mangrove forests suffered less damage than deforested coasts.

• Estuaries - many salt marshes and mangrove forests occur in or near estuaries, water bodies where river flow in the ocean, mixing fresh water with salt water. Biologically productive ecosystems, estuaries experience significant fluctuations in salinity as tital currents and freshwater runoff vary daily and seasonally. For shorebirds and for many commercially important shellfish species, estuaries provide critical habitat.

Water Pollution

The quantity and distribution of fresh water pose one set of environmental and social challenge. Safeguarding the quality of water involves another collection of environmental and human health dilemmas. Developed nations have made admirable advances in clearing up water pollution over the past few decades. Still, the World Commission on Water recently concluded that over half the world’s major rivers are “seriously depleted and polluted, degrading and poisoning the surrounding ecosystems, threatening the health and livelihood of people who depend on them”.

The term pollution describes the release of matter or energy into the environment that causes undesirable impact on the health and well-being of people or other organisms. Pollution can affect water, air or soil, and can be:

• Physical  – scientists use temperature, color and turbidity, which measures the density of suspended particles in a water sample. Fast-moving rivers that cut through arid or eroded landscapes, such as the Colorado River, carry a great deal of sediment and are turbid and muddy-looking as a result. If scientists can measure only one parameter, they will often choose turbidity, because it tends to correlate with many others and is thus a good indicator of overall water quality.
• Chemical –nutrients concentrations, pH, taste and odor, and hardness. Hard water contains high concentrations of calcium and magnesium ions, prevents soap from lathering, and leaves chalky deposits behind when heated or boiled. An important characteristic is dissolved oxygen content, which is an indicator of aquatic ecosystem health because surface waters that are low in dissolved oxygen support less aquatic life.
• Biological – is the presence of fecal coliform bacteria, which indicates contamination by human waste and suggest the presence of other disease-causing organisms. Scientists can identified biological pollution using algae and aquatic invertebrates.

 

Water pollution comes in many forms and can cause diverse impacts on aquatic ecosystems and human health:

• Nutrient pollution – is the pollution from fertilizers and other sources that can lead to eutrophication and hypoxia in coastal marine areas.

• Pathogens and waterborne diseases – disease-causing organisms (pathogenic viruses, protists, and bacteria) can enter drinking water supplies when these are contaminated with human waste or with animal waste from feedlots. Biological pollution by pathogens causes more human health problems than any other type of water pollution. Treating sewage constitutes one approach for reducing health risks. Another is using chemical or other means to disinfect drinking water. Personal hygiene is vital, as is government enforcement of regulations to ensure the cleanliness of food production, processing, and distribution.

• Toxic chemicals – our waterways have become polluted with toxic organic substances of our own making, including pesticides, petroleum products, and other synthetic chemicals. Many of these can poison animal and plants, alter aquatic ecosystems, and cause an array of human health problems, including cancer. Toxic metals such as arsenic, lead, and mercury, as well as acids from acid precipitation and from acid drainage from mining sites, also cause negative impacts on human health and the environment. Legislation and enforcing stricter regulations of industry can help reduce releases of toxic chemicals. We can also modify our industrial process and our purchasing decisions to rely less on these substances.

• Sediment – floods build fertile farmland, but sediment that rivers transport can also impair aquatic ecosystems. Mining, clear cutting, overgrazing, land clearing for housing development, and tilling of farm fields all expose soil to wind and water erosion. Some water bodies, such as the Colorado River and China’s Yellow River, are naturally sediment-rich, but many others are not. When a clear-water river receives a heavy influx of eroded sediment, aquatic habitat can change dramatically, and fish adapted to clear-water environments may not be able to adjust. We can reduce sediment pollution by better managing farms and forests and by avoiding large-scale disturbance of vegetation.

• Thermal pollution – water’s ability to hold dissolved oxygen decreases as temperature rises, so some aquatic organisms may die when human activities heat water. When we withdraw water from a river and use it to cool an industrial facility, we transfer heat energy from the facility back into the river where the water is returned. The temperature might also be raised by removing streamside vegetation that shades water. Too little heat can also cause problems.  On the Colorado and other dammed rivers, water at the bottoms of reservoirs is colder than water at the surface. When dam operators release water from the depths of a reservoir, downstream water temperatures drop suddenly. In the Colorado’s system, these low water temperatures have favored cold-loving invasive trout over and endangered native species of suckerfish.

Water

Ok, after talking a lot about soil, rocks and agriculture, let’s talk a little bit about water.

I guess it’s not unknown that even though water is abundant, the water that we can drink is quire rare. If 97,5% of Earth’s water resides in the oceans and is too salty to drink or use to water crops, than it lasts only 2,5% of the type considered fresh, which is water with few dissolved salts. Since most fresh water is tied up in calaciers, icecaps, and underground aquifers, just over 1 part in 10,000 of Earth’s water is easily accessible for human use.

Water constantly moves via the hydrologic cycle and, as it moves, it redistributes heat, erodes mountain ranges, builds river deltas, maintains organisms and ecosystems, shapes civilizations, and gives rise to political conflicts.

The freshwater ecosystems are rich in life, and they are:

• Rivers and streams – water from rain, snowmelt,or springs runs downhill and converges where the land dips lowest, forming streams, creeks, or brooks. These water-courses merge into rivers;

• Lakes and ponds – bodies of open standing water. Their physical conditions and the types of life within them vary with depth and the distance from shore.

• Marshes, swamps, and bogs – systems that combine elements of fresh water and dry land. They’re also called wetlands, and are very rich and productive.

Groundwater is very important to the hydrologic cycle because the precipitation that reach Earth’s land surface and does not evaporate, flow into waterways, or get taken up by organisms infiltrates the surface. Most percolates downward through the soil to become groundwater.

Groundwater is contained within aquifers, porous, spongelike formations of rock, sand, or gravel that hold water. The world’s largest known aquifer is the Ogallala Aquifer, which underlines the Great Plains beneath eight US states from South Dakota to Texas. However, overpumping for irrigation has reduced this aquifer’s volume by nearly 10% so far -a volume equal to 18 years’worth of the entire flow of the Coloado River.

Unfortunatelly for us, different regions of the world possess vastly different amounts of groundwater, surface water, and precipitation. However, people are not distributed across the globe in accordance with water availability. Canada, for instance, has 20 times more water per citizan than does China; the Amazon River carries 15% of the world’s runoff, but its watershed holds less than half a percent of the world’s population. Many countries like Pakistan, Iran and Egypt face water shortages.

Because fresh water is distributed unevenly in time and space, it became necessary to erect  dams to store water, so that it may be distributed when needed. In India, monsoon storms can dump half of a region’s annual rain in just a few hours. Northwest China receivs three-fifths of its annual precipitation during 3 months, when crops do not need it.

We divert and deplete surface wter to suit our needs. Water from rivers, streams, lakes and ponds are diverted to homes, cities, and farm fields. The Colorado River’s water, for instance, is heavily diverted and utilized, in a way that after all the diversions comprised, just a trickle makes its way to the Gulf of California. There are some days when water does not reach the Gulf at all. This flow reduction has altered drastically the river and its once rich delta; plant communities were modified and populations of fish and aquatic invertebrates where wipped out, devastating fisheries.

We are depleting groundwater more than surface water because most aquifers recharge very slowly. Most groundwater use goes toward agriculure. We withdraw 70% more water for irrigation today than in 1960, and since then, the amount of land under irrigation has doubled. Expansion of irrigated agriculture has kept pace with population growth. Irrigation can more than double crop yields by allowing farmers to apply water when and where it is needed. Still, most irrigation remains inefficient, and overirrigatin leads to waterlogging and salinization.

Worldwide today, 15-35% of irrigation withdrawals are thought to be unsustainable, and like Ogallala, many aquifers are being drained as water is “mined” at rates faster than it is recharged. As aquifers are depleted, water tables drop. Groundwater becomes more difficult and expensive to extract, and eventually it may run out. To make the situation even worse, when groundwater is overpumped in coastal areas, salt water can intrude into aquifers, making water undrinkable; and as aquifers lose water, the land surface aboe may subside, that’s the reason why cities from Venice to Bangkok to Mexico City are slowly sinking, while streets buckle, buildings flood, and pipes break.

Still, there are some solutions to depletion of fresh water:

• To address the depletion, we can aim either to increase supply or to reduce demand, lowering demand is more difficult politically but will likely be necessary in the long term;
• To increase supply in a giver area, people have transported water through pipes and aqueducts from areas where it is more plentiful or accessible. In many instances, water-poor regions have forcibly appopriated water from commmunities too weak to keep it for themselves. Los Angeles, for instance, grew by using water it appropriated from the Owens Valley, Mono Lake, and other rural regions of California. Becaouse of that, these area’s environments are desertified, crating dustbowls and devastating local economies.
• Desalination  also may help. The process of “making” fresh water by removing salt from seawater or other water of marginal quality. However, desalination is expensve, requires large inputs of fossil fuel energy, and generates concentrated salty waste. Over 7,500 desalination facilities are operating worldwide. Most are in the Middle East, where water is scarce and oil is cheap.
• To decrease demand farmers can improve efficiency by lining irrigation canals to prevent leaks, leveling fields to minimize runoff, and adopting efficient irrigation methods.
• Choosing crops to match the land and climate in which they are being farmed can save huge amounts of water. Crops that require a great deal of water are cotton, rice and alfalfa are often planted in arid areas with government-subsidized irrigation. In this way, the true cost of water is not part of the cost of growing the crop.