Published by Enocka Odongo, Mr. in Academic
Can a dam control both flood and drought, especially for farmers?
Farmers from my community suffer from these two extremes.
Category: Academic
Yes well designed dams can control floods to some extent. Down stream people can still get flooded when the dam operators open the spillways to avoid dam damage. If the dam height is not properly designed to take care of prolonged transpiration, operators often have no choice but open the spillways.
Drought management will also depend on the balance the designers considered in terms of water for irrigation, people and the health of the dammed river. A lot depends on how accurate the data used are the data used in dam design. The integrity of the data used in design is critical.
Published by Gordon Mumbo
Yes, DAMs help if due attention is given to their designing which considers the # of months in a year evaporation exceeds transpiration in an area where storage is foreseen as Kevin L. noted , obviously taking into account also issues associated with the soil- such as the problem of percolation. But beyond it, expensive though, it is also good to look into activities like 'Rivers Training' I.e. taking structural measures to improve rivers and their banks along River lines, as potential River bank areas (arable or those suited for grazing) are on being continuously trimmed of by either over flows or Rivers that deviate from their natural course.
Published by Teshome Soressa, National Crop Officer at FAO-Ethiopia
For farmers, low-cost water harvesting solutions might be an alternative to big dam projects.
Let us share experiences with http://smartcentregroup.com/ The nearest to you might be in Tanzania.
Published by Walter Mgina, Trainer low cost WASH Technologies
Reading through the responses (most are very good and helpful), I noticed there was only one mention of evaporation and whether evaporation exceeds transpiration throughout the year. In particularly, how many months in a year evaporation exceeds transpiration at a proposed storage location. This is a key design criteria and often determines whether a storage should be built at all. In a situation were evaporation exceeds precipitation and the storage is to be a shallow one, evaporation could remove 2-3 metres from the storage each year to evaporation with this increasing as storage reservoir reduces its volume. If 90% of the storage capacity is held in the first few metres from the surface, the losses from such a poorly designed storage would render such a structure obsolete with no net gain whatsoever to farmers, the people and state and the cost of building this structure would never be written off against benefit derived. The only way to help offset this situation is to have good evaporation and precipitation records for extended periods and only select potential structure sites that are suitable. Regards, Kevin.
Published by Kevin Linton, TopInfo - Partner
Flood control and water conservation are a multi layered endeavor. The big mistake made here in USA is centralized damming. Large construction projects, disruption of the natural flow of rivers, Slowing down the flow from rapid rivers causing sediment to be deposited at the base of the Dam. Decentralized rain water collection, home storage, cisterns, planting trees along any and all rivers and creeks. Using all waste to make and use compost. These 2 practices alone have the ability to control hundred year floods and have water at the residential level where it really belongs. Why spend $50 billion on a Dam project when $50 will do the same thing. A dam breaks lost lives and lost money. Home system breaks, nobody dies and you can fix it yourself. California has the worst flood control policies in the entire USA. Their drought is of their own legislative making.
Published by Guy McGowen, President/CEO/Chief Science Officer
see this link to a BBC story from India:
http://www.bbc.com/news/av/business-42156139/the-indian-water-mother-helping-villages
good luck!
Published by Chris Bosher
The answer is yes. Most dams in the California state, for example, serve both needs as well as wildlife protection and recreation. Federal dams on the Missouri River serve multiple needs as another example..
Published by Gary L. Guymon PhD, Profeesor Emeritus, UC Irvine, Deoartment of Civil and Environmental Engineering
Yes, a dam can help in flood control and supply the local communities with water source during the drought seasons, but construction of dam in the area of interest for Enocka would be feasible or not. As i remember that you need to carry out several studies prior to the construction: such as geo technical studies, rainfall and hydrological study and others. another question is what about the evaporation rates in the area, evaporation leads to lost of huge amount of water from the surface bodies due to high temperature,
alternative option you might consider: underground storage tanks (hand digging) , or other underground storage options, this will be like water harvesting systems
hope these information will help
Published by Zaid Rashdan, Principal environmental consultant at Al Masader Aldualiyah for environment and quality systems
Dear Mr. Odongo,
of course, it can. Depending on the geological formation and groundwater reservoir. With artificial groundwater recharge for example. We did many of those special, nearly maintenance free handled water wells. For those, you get rid of evaporation gradients and control quantity and quality of your water. We did some of those projects in Mauritania and Mali for agricultural drop irrigation and rural water supply (solar pumps)...
But please, attention, an infiltration well has different hydraulics and should be designed conform to different parameters, then correct designed water wells (the ration drill diameter to filter screen, gravel pack and a maintenance/ treatment capabilities etc. are mandatory. You can waste a huge bound of money if the wrong laptop-engineers are dealing with. Further questions are appreciated.
Published by Ulf Mischke, General Manager at WEWACO (Well and Water Consultants) Ltd.
As noted by others, well-designed dams can accomplish any or all of four objectives: (1) flood control, (2) irrigation, (3) drought augmentation, and (4) recreation. The design needs to consider all the needs of the population and the climate and geology of the area to best balance these objectives. Much of the effectiveness in drought reduction (also known as "low-flow augmentation" will depend on the topography of the dam inundation area (is it small and deep or large and shallow). This (together with humidity and geologic seepage factors) will determine how effective/economical drought reduction can be. Only a highly-experienced team of consulting engineers, hydrologists, geologists, planners, and economists can adequately evaluate your particular situation. That's why most large dam projects in the 3rd world require external funding for feasibility study, which can be several million dollars. The construction costs can go into the 100s of millions, with additional cost for irrigation canals, hydro-electric plants, etc. It can be a major undertaking, but it can change the lives of thousands or millions of people for the better. There is also a downside to the environment and relocation of indigenous people who must be re-located out of the inundation area. Good luck. Where is your project?
Published by David Boggs, Director of Environmental Services
Kenya. I have seen the farmers, including my parents suffer for many years. It is a wetland area where they farm rice and arrow roots.
Published by Enocka Odongo, Mr.
Yes a dam can help in dealing with flood as well as drought with an optimal operational policy. The flood requires allocated empty space to store flood waters but drought requires a buffer storage. The trick would be to keep allocated space empty for moderating floods during flood season but to ensure that some buffer storage is retained for dealing with drought.
Published by Vijay Kumsr, Senior Adviser at DHI Water & Environment
From dams it is necessary to refuse urgently and I know how to save water for the summer
Published by Oleg Khalidullin, Свободный исследователь at Free Expert
Yes they can survive from this two, by doing the following:
1. Awareness = educating community about the importance of water,
2. Cater all ages, culture, religion, ethics groups, schools, house to house, road shows,
3. Comply with legislation of the country,
4. Develop a master plan and implement it,
5. Strict water restrictions, and monitor it regularly, and
6. Implement water subject at all level with the schools in that country.
Published by PHETLA MANGENA, Water quality at WEB Bonaire
It depends on the dam type. Reservoir dams are mainly used to overcome the drought problem, while the retardation and infiltration dams are mainly used to control floods.
Published by Dr. Ahmed El-Rayes, Suez Canal University - Professor of Hydrogeology
while yes a dam can effectively manage water , in some countries like Yemen, Sudan, Somalia and in central Pakistan, farmer communities have organised themselves around hill torrents where they store water in farms and preserve moisture to grow crops by building mud dams before the rainy season begins , they have well developed byelaws for access to rain water from torrents and for distribution. for further study please follow the links i am pasting bellow:
http://www.ais.unwater.org/ais/mod/page/view.php?id=215
In Most of the Pakistan a well developed barrage system on rivers also divert water into canals to provide irrigation water for farming. please remember that these barrages are not dams , having limited capacity to store water and are built on rivers not hill torrents.
Published by Arshad Haroon, Strengthening Participatory Organisation - Regional Head Khyber Pukhtunkhwa
As Lippy has said, it is usual for dams to be designed and operated to fulfill multiple objectives. In such cases it is common practice to develop set of rules based on past experience. In your specific case, where the concerns are both floods and droughts, a typical solution is to keep the dam only partly full, for flood limitation, during the most of the rainy part of the year and allow it to fill completely toward the end of the rains, to have water for irrigation. This is delicate balancing act; if the rains finish early, the dams are not full for irrigation, if the rains are late the dam could be full during a flood. Kenya also has the added complication of twp rainy seasons in much pf the country. Each case has to be studied based on past experience. It depends on the costs and frequency of flood damage and the value of the irrigated crops.
Published by Ronald Manley, Partner at Water Resource Associates llp
Great. Thank you
Published by Enocka Odongo, Mr.
In Australia, most storages designed for irrigation and many for urban supply have the dual purpose of both flood and drought control. These have various amounts of success depending on such criteria as, (1) the size of the storage, (2) the years of average flow to fill that storage, (3) the size of the catchment, (4) rainfall patterns, (5) recurrent intervals to 1 in 100 years storms and (6)intensity, duration and frequency of those storms. There are other criteria, but understanding that such variables produce a multitude of different possible outcomes also underlines the necessity to engage specialist hydrologic advice with statistical stacastic modeling made available to back up any design. Please note, any large water storage should have both components for flood and irrigation supply and any storage should not be designed without both as the cost to build such structures is now astronomical. I am Lippy. Hear me roar.
Published by Kevin Linton, TopInfo - Partner
Yes a dam can control both drought and floods if welly situated and if a proper study of the drainage density and relief is done including climate history and pattern. We can discuss further on alleviation of such a problem. Email infor@sutsol.solutions or musaope@sutsol.solutions
Published by musaope mtamba, Director and Chief Consultant at Sutsol Hitech Solutions