Our farm is a tiny acreage (1.86 acres) farm. Irrigation needs are typically only from feb to jul while the rest of the year is fed by the Cauvery river and reasonably copious rains during the monsoon. 113 cms of rain fall in just 3 months. Catch it or lose it - that's basically our problem.

Some solutions essentially borrow time and energy from the future. Bore well pumps are at the highest. Ever since I've been learning about humanity's energy predicament, I have wanted to avoid bore wells like the plague. Firstly, bore wells are evil because they cause over pumping of aquifers. The encouragement we offer the system by buying a pump makes it possible for the pump seller to use a part of that earning to advertise more about bore well pumps. The people around me might also tend to copy my decisions. Hence I said “No Bore pumps at any cost”. A bore pump without electricity is as good as dead.

But so is an unmaintained, broken solar panel or wind mill.

So it looks to me that my solution must make use of what is available right now in achieving something that will need as little energy and time for maintenance in the future.

A naturally occuring pond develops clay over a period of time; The clay is formed due to microbial activity; The clay is vital to fish to cover up their eggs in the clayey bottom. The clay seals the bottom of the pond and prevents water loss to gravity. The water is rich in nitrogen content due to all the living organisms.

On the surface, a lily spreads its wide leaves to turn the problem of evaporation due to sun light to an advantage: source of energy for further growth.

1. Store water for irrigation needs during the dry-seasons (post monsoon and then pre-monsoon) by constructing one or many of
   • ponds
   • wells
   • micro-dams
   • water storage tanks
2. Conserve the constructed pits / wells / dams / hedges
3. Storing run-away water / Retrieving stored water must be doable using as little energy as possible

If rain water gets captured by the soil, gets stored as rich moisture in the mulch/soil and protected from evaporation using ground cover, only a one-time setup landscaping effort is required. Besides the fact that this will take a long time to set in, another question remains: will a landscape alone allow us to feed all the plants naturally without effort? Should water be stored? What about water for discretionary use in the distant future where the generations to come will have to learn to live a simpler, low energy life style? What is the nature of energy required to store / retrieve water?

After much brain storming (unfortunately not all of it is captured here (yet)), we decided to construct a large < 5% occupying “pond”. We ended up with a design that allows us to not only satisfy irrigation needs but also be effectively used for other things such as

• Aquaculture
  • Theft of fish is rampant in our area; Need to prevent total theft.
• Grow a diverse variety of plants and trees around the pond
  • Banks of the pond will be passively irrigated by the pond
• Unearthed soil can be used to landscape
  • We got rich red-soil from under beneficial to growing vegetables and the likes
• Can put a light pump to get water for irrigation purposes (World's greenest water pump?)
• As we foresee it, we don't need too much paddy anyway. We'd like to grow perennials which would hopefully need much lesser water going forward, leaving us to make increasing quantities of pond water available for other useful purposes year over year.

The math behind arriving at a size involved, besides other physical, easy to calculate factors, things such as budgets while keeping in mind long term stability of the pond. We constructed this pond in a three step fashion. See under Goal 2 for the list of advantages of this design.

By our math and by what the locals say, there must be water through out the year. See the spread sheet further below for actuals.

Conservation means several things. After much consideration, we came up with a three stepped design that helps conserve the pond at many levels:

1. Conserves water in three stepped rates; As the water level decreases beyond 3 ft, the surface area exposed to the sun decreases drastically. This was my original intention of this design.
2. Makes reasonably moisture ladden surface (step 1) become available for growing something
3. Structurally stabler than a simple, cost-effective yet structurally unstable underground sump design.
4. If excess soil fall occurs either due to structural faults or eroding soil, the excess will tend to remain at the top level. 8 ft space provides adequate space to hold the inflowing soil and the time to cleanup at a later point when the water has dried up.

Besides, we also intend to plant Vetiver along the edges of any surface that might be prone to soil erosion. Hopefully by end of another 2 years, erosion will be reduced to a minimum due to the wonderful vetiver!

It remains to be seen whether this goal will be met in effective ways.

Thus far, I have some experimental ideas to try but not the time to try them out. More detailed analysis is at sustainable water pump.

Pit Dimensions and volume calculations

This pic is by no means accurate or even to scale. It is just a rough idea of where we'd like the pond to be, how it would look, etc,. This is just an initial concept sketch (thanks, google sketchup!). did I already say that this diagram is no way to scale?

Of course, the trees, the 'vetiver' (see the place where water 'pours in'), the pump, the paddy, the shelter, etc., shown above are all parts of our eventual goals. There are also some parts not part of this picture, such as the 5 inlet/outlet pipes at various places. See samba09 for more details.

There are 35+ pictures showing the construction at various stages over here.

I wasn't entirely happy with how the pond turned out for multiple reasons

• The pond didn't reach the targeted volume of 11+ lakh litres owing to inability of the JCB operator to carve out what we'd wanted.
• The pond has straight line edges which looks… eww…
• Since the target couldn't be achieved, there was much lesser earth for landscaping uses. I really wanted an elevated platform in one corner to be ready for housing a shelter for the care-taker, a shelter that encourages my family to visit and stay in the farm often and be ready to achieve my dream had we achieved this target.

However, nothing much can be done now. Cauvery will reach soon. We also got…

• Lots of red-soil; Not some “junk” soil that I thought we might hit. I thought the only use of this soil would be for landscaping / elevating. Great that it can be useful for growing other non-paddy crops
• Lots of gravel at the bottom which is much desired for water retention; As shown in the pic, there was water staying at 11 ft deep for over 2 days after a moderate rain. The varappu built out of the unearthed gravel will likely be stronger
• People also appreciated the stability of this pond due to its three stepped design
• Locals also said it would be useful for people who might not be able to see the pond's boundaries during excessive flooding to realize a “warning” of sorts at the 3 ft depth.