Today CDI is implemented on an area of 24 ha (flat arable land) at Ragnabo Farm. It takes very little work to keep it in operation as basically only supervising is necessary. This page discuss implementation details, drainage design architecture, combining multi functions controllers, map info, old drainage systems and energy, CDI effect on nitrogen leaching plus opens up for future plans of continuing work.

How to implement CDI:
The existing drainage system map, if available, is a good start. This map Controlled Drainage & Irrigation (Google Map) shows how the CDI technique has been implemented on Ragnabo Farm. The CDI additions can be seen as makers in map. They show where suitable places for implementing control structures can be located. To save cost it is recommended to re-use (if available) and re-build existing structures such as sludge wells and convert them into a control structures. Detailed description on CDI as well as result can be found here (pdf): Agricultural Practices to Prevent Eutrophication.



How to decide on location for structure position:
Besides map of the drain system a topology map is also very helpful since control structures should be placed at low elevation points. One should also seek drain node points in map because this will create a large service area for one specific control structure. At the same it is necessary avoid places that will be in conflict with farming transport and machine operations. So in the end it is a compromise, sometimes you even need to move existing node points to field boundary because of practical reasons. In average you can serve about 1.3 ha per control structure, more if very flat land.

Make plan for three-functioning system:
Remember that the earlier water management architects (our 'farm ancestors') only planned for 1st. function: the out-drainage function. Now you have to plan for adding function number 2: To dam up the water. And optionally also plan for adding function number 3: To irrigate (also called sub-irrigation) the land. All 3 functions can be fulfilled in the same control structure as shown in picture to the left. It saves cost, reduces hardware and simplifies management. Note that irrigation requires that water is available during the dry season, either from a pond or a creek.





Map information:
To implement CDI you need fully information of how existing drainage lines are located but also in what condition there are in. If they are not good they have to be replaced or reconditioned. If not known they have to be located. You are helped with the fact that they have not moved after being placed in soil some long time ago, so old maps are a good source for info. If no maps exist then it takes some extra cost to find out. Or you could skip and make a completely new system. It is also advantage if you know how soil surface respond heavy rainfall as well as dry periods. It affects tile drains spacing and depths. Most important is to have full knowledge around the node points. Generally irrigation requires less depth than controlled drainage, for example 50-60 cm. If placed deeper the response time gets to long as you probably need to adjust for possible upcoming heavy rainfall. Watching the daily weather forecast is therefore important.

CDI Results:
Here are some nutrients balance and nitrogen leaching results (pdf): CDI results.
Results shows high effectiveness in using nutrients (=low on surplus nutrients) and low values on nitrogen leaching compared to a similar farm.

Old drain systems:
It is sometimes necessary to know about old and obsolete systems that are still functioning as they can have an negative impact on the new functions you are building with the control structure. If so they have to be accounted for. For example an unknown stone ditch passing through closely to a drainage control structure will be devastating for the damming function as it will open up for water leakage around the dam without you knowing about it. The leakage must be stopped, for example by taking away some sub-surfaced stones in that old drain. Unfortunately there has been a normal historically common practice when establishing new drain pipes to destroy earlier drain systems or just skipping the existence of them. When you only had to consider the out drain functions it did not matter.
Drainage History 1981 to 2015  (pdf) shows modification made to the system between years. The yellow lines were added after 1981. And also many of them were added because of no knowledge about earlier systems, such as in the fields in north east. As a consequence the yellow drains destroyed the older cyan colored drains seen in picture.
About old systems, the worst case at Ragnabo Farm is a spot that have 4 layers of drain systems. Today all old and feasible drain lines have all been incorporated into current drainage system.

Energy considerations and future plans:
CDI opens up for cost efficient and low energy sub-irrigation as it can be made automatic and made continuously operational on 24 ha, 24 hours a day, 7 days a week without any work or moving of machines. The energy consumption is about 1000 kwh per year for the CDI.

Plan exists to install a distributed observer system that reports current status, such as water table level, to a web portal via a telecom system. Portal could be located as an app in a smart phone which will become handy when supervising the system either remotely or on site. Also the controller reference points are planned to be adjustable remotely. Power can be taken form solar energy. This will then create a fully controllable and observable system for water management. Technology and competence is available.