A Check dam is a small dam constructed to counteract erosion by reducing water flow velocity. Check dams are an ancient technique dating all the way back to the second century A.D. Check dams are typically implemented as a system of several check dams situated at regular intervals across the area of interest. Each check dam retains soil that would otherwise be lost to erosion. The reservoirs create a deep pocket of damp soil that can support deep rooted trees even after the water has all soaked in. These interactive maps can help identify good locations to install check dams.
Each Dam location map renders a red square pixel for each location where it identified sufficient accumulating water to fill a reservoir from each storm. Dark Blue Pixels represent the watershed for the currently active DAM while the light blue shows where the water will drain next.
The Reservoirs sizes are based on 7mm or (0.28 inch) of free runoff from a storm. The first portion of water from each storm will be absorbed into surface soil so even if a storm drops 1/2 inch of rain it may only produce 0.28 inch of free runoff. Any low lying areas must fill before any runoff will leave the immediate area.
This analysis is based on NASA SRTM DEM data. Each DEM is built around a rectangular grid of elevation readings. We receive basic elevation data is supplied by NASA SRTM V3 is the the average of all readings in the cell. The NASA data is supplied in in approximately 30 meter grid so each cell represents approximately 30 meters X 30 meters or 900 sq meters. 10 mm of rain in 900 sq meters provides 2,379 gallons of water. For fine grained analysis such as placing dams for single farms requires a smaller grid such 1 X 1 or 3 X 3 meter is used to allow more refined placement. Contacts us for additional detail on how we can help build more precise DEM grids.
Ground water on islands is supplied by a fresh water lensthat floats on top of a layer of salt water. Over pumping ground water on islands is dangerous because it allows saltwater to intrude into freshwater zones. This can cause previously good wells to start producing salty water.
Maximizing the amount of rainfall absorbed into the aquifer helps rebuild the freshwater lens and is far less expensive than installing desalination facilities.
Rodrigues island is occupied by about 80,000 people most of whom are poor farmers. Many of these farmers are loosing over 80% of their farm income due to water scarcity caused by changing water patterns. Building many small check dams on their individual farm parcels can dramatically improve their food production and carry capacity. dramatically improve food production.
Catalina is always balanced between providing the water needed by residents and tourists while avoiding over pumping of their aquifer. By adding check dams they can dramatically improve their aquifer recharge rate and worry less about providing adequate water.
Catalina has already invested in limited desalination but it would be far more cost effective to add thousands of small check dams that would help increase the amount of water available in their aquifer. Catalina island may need both approaches but they should maximize use of the less expensive approach first.
Our Analysis with check dams sized for 124,000 gallons each there are locations to build 2,225 check dams. This would impound 276 million gallons of water per storm most of which would soak in and recharge their aquifer. Any infrastructure that installs wells on a island with re-occurring droughts will benefit form increased aquifer recharge. In reality this number of dams would be overkill but adding some number of them would improve village resiliency and manage the risks of natural hazards and climate change as per the World bank program goals.
The 276 million gallons is based on 7 mm of free runoff. Weather records show these islands receive about 1300 mm even during El Nino years and closer to 2500 during La Nina years. Based on this we could expect the reservoirs to refill over 100 times per year increasing total ground water recharge to over 27.6 billion gallons per year.
Climate change and the associated rise in sea level will mean that the extra freshwater recharge into their freshwater lens will be critical as it can help reduce the impact of saltwater intrusion by providing a larger amount of fresh water displacing the underlying salt water.
The Nanngu may actually be on Nendo island and they appear to have built an above ground water catchment about 3 miles from the village and ran pipe from there. This analysis may be a good way to implement similar programs by helping to find the easiest places to build similar catchment.
Some remote Solomon islands last had running water 20 years ago. Solomon Islands National Infrastructure Investment Plan
Our analysis with 99,000 gallon reservoirs shows that Tuvalu could install 84 check dams that could store a total of 8.34 million gallons of water per storm. The island is so small that we would want to run an analysis with a 3 meter DEM grid to better position the reservoirs. Weather records indicate Tuvalu receives over 200 mm of rain even during their dry months and over 375 mm during their Jan and Dec. The 99,000 gallon refill is based on 7 mm of run off so the reservoirs should recharge at least 20 times per month. This would add up to 166.9 million gallons per month most of which would end up percolating into their freshwater lens.
During the Dec-2015 and Jan-2016 they had floods so bad they showed boats being used in the city. Less than 1 year latter they are faced with severe drought and water scarcity bad enough to require water rationing.
Flooding like this occurs when rain falling on surrounding hills during major storms accumulates too fast and causes a phenomenon similar to flash floods. Check dams are well proven mechanism with over a 2000 year history that can solve the problem. Our approach can also improve food production and carry capacity.
In an area with regular re-occurring floods that also experience re-occurring drought the perfect solution is to store more watter on the land where it falls so it can recharge the local aquifer while slowing the flow down for long enough to allow down stream drains to function as designed.
The most common approach of large dams is problematic due to impact, cost and planning overhead. Thousands of small check dams can be built inexpensively by hand using mostly rock and sand. These Interactive Maps show the terrain surrounding La Pas is ideal for check dams.
This process can make the area surrounding the factory more pleasant. It can also reduce flooding risk at the factory and reduce the factories dependency on city water. It can also to support growing trees and increasing biodiversity near the factory.
The process offers Tesla a perfect opportunity to add sustainable / renewable water to the mix of renewable and sustainable technologies they are demonstrating. We can expect future Gigafactories to face push-back about water consumption and this process allows Tesla to defuse that objection before it is even raised.
Tesla purchased an initial 900 acres and holds options to purchase an additional 9000 acres for wind farms. This means he will likely control 9,900 acres. A single 0.28 inch of free runoff from land this size is enough to capture 67 million gallons of water. Weather records for Sparks show 8 months per year deliver more than 0.6" of rain which would be sufficient to refill reservoirs designed to capture the first 0.3" of rain once per month.
This process offers Tesla the opportunity to demonstrate collecting the majority of all water consumed in the factory from the surrounding land. In the Tesla scenario it would make the most sense to install as many 0.15 acres check reservoirs as possible to support local plant growth and animals then install several 1,000 cell (222 acres) reservoirs to provide liquid water for the factories and recreation. The water from the 1,000 cell reservoirs would be piped into filtration units where it can be treated to meet the standard required for their process.
In this region we can easily support one tree per 0.15 acres with very small check dams. If implemented across the majority of the land Tesla controls it could yield 66,000 trees each of which is capable of producing about 100kg of biomatter per year. The trees could be harvested as lumber but could also be used to convert via digester into alcohol. Tesla could demonstrate growth of sufficient biomatter to allow large scale conversion needed to use as an enabler for the transport industry. This fits well with their long term vision because high efficiency low emission generators burning alcohol are an nearly ideal backup for storage from battery banks. It is a perfect way to offer extended storage capacity at sites where meeting the entire demand from battery is not cost effective. These trees can also be converted to methane which can be used to directly power modern fuel cells.
Circle ranch occupies 32,000 acres in a very dry portion of Texas. The owner Chris Gill is applying holistic methods for habitat rehabilitation. These include animal grazing patterns that mimic natural buffalo herds. Keyline subsoiling plow techniques and many others intended to slow the movement of water down so it has time to soak into the surface soil. He is an advocate of maximizing species diversity as a way to retain ecological balance.
Micro check dams appear to be an ideal addition to holistic land management. A Check dam is a small dam constructed to counteract erosion by reducing water flow velocity. Check dams are an ancient technique dating all the way back to the second century A.D. Check dams are typically implemented as a system of several check dams situated at regular intervals across the area of interest. Each check dam retains soil that would otherwise be lost to erosion. The reservoirs create a deep pocket of damp soil that can support deep rooted trees even after the water has all soaked in.
Our analysis can help Circle ranch identify locations to build thousands of small check dams along with a few larger check dams. The small reservoirs help increase food availability while the larger dams provide watering holes
The benefit of the check dams for Circle ranch is that grass will also volunteer in the damp soil collected by the dams creating many pockets of additional feed that grow even during drought years and grow actively deeper into the dry season. We believe this can increase the ability of the land to feed animals. The dams and reservoirs are small enough that they should not affect the application of other holistic techniques. Each reservoir can be planted with fodder producing deep rooted trees. These trees will receive a regular water supply due to the concentrating effect of the reservoir. The consistent water will allow them to produce a full load of edible fodder even during drought years.
Some private wells have already been affected by saltwater intrusion but the USGS hydrologists said such cases appear to be isolated and are not likely to increase.
With continued high density development we can expect more demand in a concentrated
area to place further stress on the aquifer. The USGS claims the aquifer
can sustain the demand but many private land owners have already been
affected by failing wells even if the wealthy city can afford to tax
and drill deeper wells.
Active Groundwater studies
While the collaboration between local government and land developers doesn't appear to
rise to the level demonstrated in Flint Michigan. One does have to wonder how many people
publishing the official report have paychecks that benefit from higher population density
caused by high density development even as they are incurring hundreds of millions of dollars
of liability due to infrastructure, schools, roads and water impact they are not forcing the
developers to pay for. If the cities increased pumping to service these high density developments
has any possibility of causing the failure o reduced water quality from existing private wells
the developers should be forced to buy 20 year indemnity bonds to pay for the damage. Otherwise
their profits now are being funded on the backs of other private land owners.