LAKES AND ALL KINDS OF THEM

Lake is one form of terrestrial waters that is often encountered. In simple terms, lakes can be interpreted as basins on the surface of the Earth which are usually bowl-shaped naturally filled with a collection of water (generally fresh water) in relatively large quantities. Most of the water sources that fill and provide water supply to the lake come from rainwater and river flow that empties into the lake. Springs and ground water can also fill the lake. In such cases lakes are generally permanent, meaning they remain filled with water throughout the year. Conversely, if the water source of the lake fill is only one kind, such as from rain water, then generally the lake is temporary or periodic. So, the lake can dry at certain times.

Based on the type of water, the lake can be divided into two, namely as follows.

a.       Saltwater Lake. Generally saltwater lakes are located in semiarid or arid areas, where evaporation occurs which is very strong and does not have an output stream. If this kind of lake becomes dry, then the remaining layer of salt in the bottom of the lake. Many temporary lakes are found in the arid region which has high salinity. Examples of saltwater lakes are the Great Salt Lake in America and the Dead Sea in Jordan.

Great Salt Lake

Object Source: https://www.youtube.com/watch?v=pIJvh8GiyKc

b.      Freshwater lake. This lake is mainly located in humid (wet) areas that have high rainfall. In general, these lakes get water from rainfall and always drain the water to the sea. So this lake is an open lake. Almost all Indonesian lakes are freshwater lakes.

According to the process of formation, the lake can be divided into several types, namely as follows.

a.       Tectonic Lake, which is a lake formed by the presence of tectonic processes that cause dislocation of rock layers, such as folds and faults. On the surface of the Earth that has decreased is filled with enough water (rainwater, rivers, springs) so that a lake is formed. Examples of tectonic lakes located in Indonesia are Lake Poso, Singkarak, Tempe, and Tondano. An example of a tectonic lake outside Indonesia is Lake Tanganyika in East Africa.

b.      Volcanic Lake, which is a type of lake located on the former crater hole of a volcano, so the lake is formed due to volcanic activity. In the former a volcanic eruption there will be a basin called volcanic depression. If the bottom of the basin is covered by water-resistant volcanic material, falling rainwater will be accommodated and form a volcanic lake. The shape and extent of volcanic lakes is influenced by the type of volcanic process that forms them. The type of volcano maar will form a maar lake. In volcanoes with eruption of the caldera, extensive caldera lakes will form. Examples of volcanic lakes are Lake Kelimutu, Kerinci, Rinjani, Telaga Warna, and Lake Batur.

c.       Lake Tecto-Volcanic, which is a type of lake formed by a combination of tectonic and volcanic processes, for example Lake Toba.

Lake Toba

Object Source: https://www.youtube.com/watch?v=-UNn0YKpdoU

d.      Karst Lake (Dolina), which is a lake that can be found in limestone / karst regions as a result of the dissolution of limestone that forms water filled basins. Generally in the form of small lakes that are temporary. If at the bottom and dolina cliffs there is a clay material which is a waterproof material, then the falling rainwater will be accommodated in dolina and cannot continue to enter the limestone so that dolina lake is formed. Dolina lakeccan also occur due to the presence of high water in limestone soils. Actually the limestone is not translucent, but because it has regular gaps, the rainwater that falls still enters and seeps down. If the soil layer below the limestone layer is a waterproof layer and the rainfall in the area is large, then the water stored in the limestone layer is high enough so that the bottom of dolina can be inside the karst water surface.

e.       Glasial Lake, which is a type of lake formed by erosion by glaciers. Glacial lakes are found in regions around the polar climate. After the ice age ended, the areas that the glaciers had once passed through became dry and filled with water. If the valley that contains water is not related to the sea, then the valley will become a lake. Examples of glacial lakes are Lake Michigan, Lake Superior, and Lake Ontario that are between Canada and the United States.

Lake Superior from above

Object Source: https://www.youtube.com/watch?v=Ekgic7aHc50

f.       Cirques are lakes whose water comes from melting ice. Cirques can be found in high mountain areas where some of their bodies are covered in ice mass.

Cirques Lake in Callaghan National Park, Canada

Object Source: https://www.youtube.com/watch?v=5fN9Iu3aclM

g.      Stoppable Lake, can be formed when materials such as mountain debris or lava flows that stem the river valley, so that the flow of water will be restrained and eventually form a lake. Here also includes artificial lakes called Dams / Reservoirs, for example Gajah Mungkur Reservoir in Wonogiri, Central Java and Jatiluhur Reservoir in West Java.

Gajah Mungkur Reservoir

Object Source: https://www.youtube.com/watch?v=7mKodBqJkl4

One pool of Gajah Mungkur Reservoirs

h.      Lakes due to river erosion, for example horseshoe lakes.

The process of forming horseshoe lakes

Object Source: https://www.youtube.com/watch?v=4qKS_Nk7UmY

Presented by

Mockup Betterpad-Ray Libraripedia

(Benteng Terpadu Raya/Great Integrated Fortress)

Reference:

·         Wardiyatmoko, K. 2004. Geografi SMA Jilid 1 untuk Kelas X Kurikulum 2004 Berbasis Kompetensi. Jakarta: Erlangga.

·         Utoyo, Bambang. 2009. Geografi 1 Membuka Cakrawala Dunia untuk Kelas X Sekolah Menengah Atas/Madrasah Aliyah. Jakarta: Pusat Perbukuan Departemen Pendidikan Nasional.

·         Soegimo, Dibyo and Ruswanto. 2009. Geografi: untuk SMA/MA Kelas X. Jakarta: Pusat Perbukuan Departemen Pendidikan Nasional.

·         Rahayu, Saptanti and friends. 2009. Nuansa Geografi 1: untuk SMA/MA Kelas X. Jakarta: Pusat Perbukuan Departemen Pendidikan Nasional

PHYSICAL QUALITY OF RIVER WATER AND ITS VARIOUS UTILIZATION

River is one of the natural resources which is a gift from God to fulfill the life needs of humans and living things on Earth. But today, the benefits of the river are decreasing because many rivers have been polluted due to human activities, for example due to industrial waste, household waste, agriculture, and oil waste. According to the story of parents/old man that in ancient times, when river water had not been polluted, people around the river used to use the river for their daily needs, such as the need for clean water for drinking, bathing and washing. Besides that the river is also a source of freshwater fisheries. Therefore, there are many traditional residents villages along the river. At present it is rare to find people who use river water directly, except in certain areas such as the islands of Borneo (Kalimantan) and Sumatra.

The quality of water for living needs must meet health standards, especially for drinking water. The requirements of good drinking water are to be clear, colorless, odorless, and there is no content of organic substances that cause disease. Today, taking river water for drinking is dangerous for the body. In modern settlements, river water for drinking water needs to be processed first through cleaning and screening conducted by Drinking Water Company (PAM in Indonesia).

One country that has many rivers is Indonesia. There have been many mass media that discuss the quality of rivers in Indonesia. River water quality in the most densely populated island in Indonesia, Java, especially in large cities such as Jakarta, Bandung, Tangerang and Surabaya tends to decline. Decrease in river water quality can be seen by changes in the levels of certain parameters such as pH levels, Dissolved Oxygen (DO) levels, Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). BOD and COD parameters of riversin all provinces in Java that have exceeded the specified quality standards, including the Ciliwung, Sunter, Citarum, Kaligarang, Bengawan Solo, and Surabaya Rivers. Basically there have been efforts to normalize a number of these rivers, but they cannot be said to be successful. This must also be supported by the community to help preserve it.

The degree of acidity or pH is a chemical quality criterion. Good water must be neutral (pH around 7), so there are no pollutants that change the nature of water to acid or base. According to the Decree of the Minister of Environment (Indonesia) No. Kep-03 / MNKLH / II / 1991, February 1, 1991 stipulates that factory wastewater can be disposed of into the river if the pH of wastewater ranges from 6 to 9. BOD is the amount of oxygen needed to degrade (break down) organic waste, while COD is the amount of oxygen which is needed to break inorganic waste.

If a lot of water contains organic waste, the amount of oxygen needed by microorganisms to degrade the waste will be large, and means that the BOD number is high so that the DO rate is low. With the amount of oxygen to degrade waste, the dissolved oxygen level in water will decrease. The same thing happens if the COD number is high. Waters with high BOD usually cause unpleasant odors. If the BOD number is high and the DO rate is low, the degradation of organic waste will be anaerobic (without oxygen). Anaerobic processes are oxidations that do not use oxygen to produce NH₃, H₂S, CH₄ compounds that smell bad. The high number of BOD and COD and the low DO numbers make it difficult for animals and aquatic plants to develop, even die.

Turbidity of the Bengawan Solo River from Above

Object Source: https://www.youtube.com/watch?v=O6OUh8NQ7Y0

Bengawan Solo Upstream, Kali Wiroko in Wonogiri regency, has experienced excessive sedimentation. This river water flows to Gajah Mungkur Reservoir and towards Bengawan Solo

Object Source: Personal Documentation

Water turbidity in rivers on the island of Java generally shows a fairly high level. Estimates of the amount of mud carried by rivers on the island of Java can reach 25 million tons per year. This indicates that soil erosion has occurred in the upstream section.

The regulation of river use is important because it is related to the pollution threshold value. The basis for determining river benefits is the dominance of utilization in the region, based on the quality of river water at that time. Water users and those who potentially pollute water must play an active role in maintaining and utilizing river water well and are expected to overcome water quantity and quality problems. Prokasih's effort (program kali bersih/clean river program) in Indonesia is one of the efforts made to overcome river pollution. This program is a centralized activity and aims to reduce the amount of pollutants entering the river, so that rivers can be used properly and safe for life.

Rivers have benefits that are very important for human life, for example as follows.

a.       The river contains many building materials such as sand, river stone, and gravel.

Merapi Volcano Sand collection activities in Klaten regency, Indonesia

Object Source: https://www.youtube.com/watch?v=5JYOpeX3s7o

b.      Rivers can provide livelihoods for residents such as sand collection, rocks, looking for gold ore, diamonds, alluvial tin, and fisheries.

c.       Waterfalls on rivers can be used as power plants.

d.      Rivers can be used for irrigation needs, for example by making dams or reservoirs. With the existence of a dam, a hydroelectric power plant can also be built. Examples of reservoirs are Gajah Mungkur Reservoir in Wonogiri, Central Java, and Jatiluhur Reservoir in West Java.

Gajah Mungkur Reservoir in Wonogiri which functions as a hydroelectric power plant

Object Source: https://www.youtube.com/watch?v=7mKodBqJkl4

e.       Can increase soil fertility because the river contains many minerals that are needed for plants.

f.       The result of sedimentation of the river can be a fertile alluvial plain.

g.      Rivers have an important role for the survival of an industry that requires a lot of water, for example the brick industry, tiles, and others.

h.      Rivers as a means for traffic by water transportation. This is common in areas that have large rivers, such as in Kalimantan (Borneo), Sumatra, and Papua. Examples of these rivers are the Kapuas, Barito, and Musi rivers.

i.        Freshwater fisheries.

j.        Water recreation and sports.

Reference:

·         Wardiyatmoko, K. 2004. Geografi SMA Jilid 1 untuk Kelas X Kurikulum 2004 Berbasis Kompetensi. Jakarta: Erlangga.

·         Utoyo, Bambang. 2009. Geografi 1 Membuka Cakrawala Dunia untuk Kelas X Sekolah Menengah Atas/Madrasah Aliyah. Jakarta: Pusat Perbukuan Departemen Pendidikan Nasional.

·         Soegimo, Dibyo and Ruswanto. 2009. Geografi: untuk SMA/MA Kelas X. Jakarta: Pusat Perbukuan Departemen Pendidikan Nasional.

·         http://www.bintangmedia.id/indikator-kualitas-air-ph-bod-do-cod/

EXPLANATION OF WATERSHEDS

Watersheds are formed from a collection of rivers in a basin system with a outflow or single estuary. Watersheds are water container areas that enter into larger river water areas and end at an output (estuary). The watershed area boundary is measured by connecting the highest points between the watershed with one another. Between one watershed and other watersheds are usually restricted by ridge paths in the form of hills or mountains. The two boundary areas of the watershed are known as the River Flow Limits.

Many watershed areas in Indonesia are now in critical condition. Some forest areas, especially in the upper reaches of the river, have turned into shrubs, even bare or almost without trees. Until now the watershed damage continues.

The problem of watersheds in Indonesia is now mostly focused on floods that repeatedly afflict areas that occur in the lower / flat areas. This not only caused land productivity to decline, but also caused problems of deposition of mud and soft sand in reservoirs, irrigation canals and hydropower projects. This is a result of inappropriate land management, such as shifting cultivation and dryland farming, without proper conservation treatment and does not follow land use patterns.

So, to cope with floods, in the upstream area there must be a lot of plants or vegetation because of the position of the upstream area as a buffer zone. This needs to be maintained so that water flows remain (balanced), both in the dry season and in the rainy season. In addition, to maintain the balance of the watershed ecosystem, it must also be considered the problem of waste, both household and industrial waste.

The factors that affect the watershed are climate, the type of rock that the watershed goes through, and a lot of water falls into the groove during rain. Whereas fast or slow rain water collected in a groove is strongly influenced by the shape of the slope of the watershed. Within the watershed area there are natural forms such as meanders, floodplains and deltas.

Calculation of the amount of rain in a watershed can be done using two ways, namely:

1.      Isohyet, used when the watershed area is greater than 5,000 km2. Isohyet is a line in a map that connects places that have the same amount of rainfall in a given period.

2.      Thiessen, used if the watershed is not elongated and narrow, with an area between 1,000 - 5,000 km2.

Isohyet

Object Source: https://www.youtube.com/watch?v=n9eKQQiD86Q

Thiessen

Object Source: https://www.youtube.com/watch?v=ztiBYCMY4PI

The watersheds are divided into three, namely in the upstream area of ​​the river, the middle river area, and the downstream area of ​​the river.

Generally, the watershed in the upper reaches of the river is hilly and steep, so many rapids and waterfalls are found. Upstream river valleys generally resemble the letter V with steep cliffs, because the river flow is still very heavy so that the erosion process erodes into the riverbed. Around the river body there are many large and relatively pointed boulders. This area is widely used for vegetable fields, plantations, or forests which are buffer zones. Around the river there are residential settlements.

The watershed in the middle of the river, the situation is in the form of a relatively flat sloping area so that transportation and communication routes are relatively easy. The sloping area conditions allow the erosion process to take place vertically and laterally in a balanced manner, so that the shape of the valley usually resembles the letter U. Around the river body there are many stones whose surface is relatively round and not as large as upstream rock. Stones whose surfaces are relatively round occur due to polishing by material transported by river water, especially gravel and sand. In the middle area there are rarely found rapids or waterfalls, even none. This area is a place of population activity.

In the downstream area, the watershed is a sloping and fertile area. Therefore, this area is widely used for settlements and agricultural areas (for example rice, corn, and coconut). The area is very flat and approaching the river mouth. River water flows very slowly and many meanders are found. Horseshoe lake (oxbow lake) that is cut off meander flow can be found in the downstream area. The downstream area is a vast flood plain and the shape of the valley is very wide. Downstream there are also many river banks as a result of sedimentation of mud and soft sands.

In Indonesia, there are many disasters related to rivers, such as floods. Floods occur because there is damage to the function of the river. This is a sign that the condition of the Watershed is also problematic. Development that is not in accordance with the environment is the cause, but there is no total problem solving and the integration between parties is not good. According to the KLHK (Ministry of Environment and Forestry) Minister, Siti Nurbaya, once stated that 2,145 Watersheds in Indonesia must be restored. There needs to be strategic and concrete actions from various parties to restore a damaged environment.

Environmental sustainability will benefit all parties. If the Watershed can be restored, it will be able to support the resource needs of both current and future generations.

Wiroko river (one of the upper reaches of Bengawan Solo, the largest river in Java) during the rainy season

Wiroko River during the dry season

Reference:

·         Wardiyatmoko, K. 2004. Geografi SMA Jilid 1 untuk Kelas X Kurikulum 2004 Berbasis Kompetensi. Jakarta: Erlangga.

·         Rahayu, Saptanti and friends. 2009. Nuansa Geografi 1: untuk SMA/MA Kelas X. Jakarta: Pusat Perbukuan Departemen Pendidikan Nasional

·         Utoyo, Bambang. 2009. Geografi 1 Membuka Cakrawala Dunia untuk Kelas X Sekolah Menengah Atas/Madrasah Aliyah. Jakarta: Pusat Perbukuan Departemen Pendidikan Nasional.

·         https://news.detik.com/kolom/d-4436027/integrasi-pengelolaan-daerah-aliran-sungai

UNDERSTANDING THE RIVER AND THE PROCESS OF FORMING A RIVER VALLEY

River is fresh water that flows from its source to or empties into a sea, lake or larger river. These rivers lift various materials and continue to be deposited. As a result of this process a river valley is formed, which is a lower surface form than other parts produced by erosion of water or river erosion.

River erosion or can be called ablation (erosion by water) is the event of moving a rock or soil caused by continuous river water flowing. Basic erosion is erosion that occurs at the bottom of the river which will cause the riverbed to become deeper. Edge erosion is erosion that occurs on the banks of the river which will later cause widening on each side of the river.

River valley in the Grand Canyon

Object Souce: https://www.youtube.com/watch?v=ezpqDi42pRM

There are several stages that can explain the erosion by river water flow:

1. Flowing river water creates friction on the ground. And the size of the friction that occurs is influenced by the size of the flowing water.

2. Friction is greater if the speed and amount of water are also getting bigger.

3. The water speed is also greater if the gradient or slope of the land is getting bigger.

4. Friction between water and solid objects that are transported by water with soil or rocks at the bottom of this can cause erosion.

The process of river valley formation takes place through three processes, namely deepening, widening, and elongation.

a. Deepening of the river valley

In the upper reaches of the river, the erosion process is very strong because the height difference is very high. High flow speeds cause the process of erosion and transportation to work more dominantly. Its erosion power works by mashing and grinding the riverbed called hydraulic erosion. Then followed by mechanical erosion, the rock debris carried by heavy flow also erodes and accelerates the deepening of the channel. In addition, chemical erosion also occurs, namely the dissolution process and acid reaction to the bottom and edge of the river channel

b. Widening of the river valley

In flat areas, the most dominant erosion process is lateral erosion due to the slow speed of flowing water. Its nature widens the river valley channels. There is also the process of adding deposits from material wasting (mass wasting) on the slopes above which is called the agradation process which helps accelerate the widening of the river valley.

c. Elongation of the river valley

This event occurred because of a decrease in sea level, so that land increased. And because of the growth of the delta, the land face also increases. Delta is sediments in river mouths originating from land, sand, small rocks, and various materials carried by the river flow to the edge of the sea.

Delta Formation Scheme

Object Source: https://www.youtube.com/watch?v=XINpPb8XwJU

If the amount of damage carried by the river water flow is very much and can not be carried away by water again, then the results of weathering carried by the water will accumulate somewhere. Here the erosion stops, but is followed by erosion to the side. So a river that initially flows rather straightly turns and forms meanders. Because of the meanders, the river valleys became wider.

Meander

Object Source: https://www.youtube.com/watch?v=4qKS_Nk7UmY

The development of a river valley shows its age. Age here is the relative age based on the appearance of the shape of the valley that occurs in several stages (stadium). At the beginning stage, the river gradient is still large so that the vertical erosion power is large. At this stage the original plain has just been formed. This can be caused by the removal of the seafloor to the surface or eruption of volcanoes which produce very much sedimentation so that new land surface is formed. In some places there are beginnings of rivers with small valleys. So at this stage the surrounding area is still a between streams and erosion is just beginning to occur.

The river flow is divided into two, namely the young and adult stadium rivers.

The characteristics of the young stadium are as follows.

1. Cross section of a V-shaped valley. This occurs because of the strong vertical abrasion due to the large gradient.

2. Many rivers still have temporary base erosion.

3. Transport of rivers is large.

4. The width at the bottom of the valley is equal to the width of the river channel.

5. The bottom of the valley is not even.

The characteristics of the adult stadium are as follows.

1. The river gradient is smaller.

2. Lateral or side erosion. While practical vertical erosion has not occurred.

3. Has undergone riverbed leveling.4. The valley forms the letter U, whose width exceeds its depth.

5. At the valley floor there is a flood plain and on a plain flood the river forms meanders.

6. There is no basic erosion so that the river valley bottom is evenly distributed.

Reference:

·         Wardiyatmoko, K. 2004. Geografi SMA Jilid 1 untuk Kelas X Kurikulum 2004 Berbasis Kompetensi. Jakarta: Erlangga.

·         Rahayu, Saptanti and friends. 2009. Nuansa Geografi 1: untuk SMA/MA Kelas X. Jakarta: Pusat Perbukuan Departemen Pendidikan Nasional

·         https://ilmugeografi.com/geologi/erosi-sungai

·         https://ilmugeografi.com/ilmu-bumi/hidrologi/pengikisan-oleh-air