Re: [Sarnissa-french-aquaculture] [Sarnissa-african-aquaculture] monks and standpipes

Dear Raymond, Karen and Adrian Adrian you are spot on. Just to add yet another advantage of monks! The capability of disposing of colder water at the pond bottom should there be appreciable new water input - rainfall or new water exchange - into the ponds, that's apart from Adrian's three well put advantages of monks. The monk boards can also be so configured so as to remove bottom water from ponds. Obviously a mesh screen needs to be included in the configuration. A bottom drainage configuration of the monk boards is particularly useful in duckweed culture ponds/lagoons where floating duckweed biomass is not lost during periods of monk overflow caused by rainfall and/or surface run-off. The key to designing the correct monk size, and here I'm referring to the internal width of the monk, is to understand the volume of water entering the pond - sum of rainfall and run-off water - then decide on the maximum allowable height of overflow water discharge over the internal crest width of the monk that you will tolerate given the allowable freeboard (difference between pond water height and the dike/levee crest) in the ponds. The monk overflow discharge formula (neglecting approach velocity in ponds on purpose) can be approximated using the below formula; where Q = Water overflow discharge over the crest of the monk boards, m^3/sec B = internal width of the outlet monk, m H = head, the difference between the pond water level and the monk board crest, m Now all one needs to do is marry the monk (if this is permissible!!!) to the right pipe diameter size to cater for the volume of the allowable discharge overflow which is quite straight forward. I've attached an article from Fish Farmer issue 21 which I think originated from the 1970's as well as a one page set of drawings showing the position and concept of monks in ponds from literature which originated from the Jonkershoek Fish Hatchery where Dr. Douglas Hey had some input (my days at Jonkershoek with Cape Nature Conservation in the late 1980's). I've also added a page giving four monk sizes, viz. internal width's of 0.35m, 0.5m, 0.75m and 1m showing the overflow discharge volumes in m^3/sec against the depth difference between the pond water level and the that of the overflow water over the monk board crest. The article in the Fish Farmer (21) also describes wooden monks which is also an option for resource limited farmers perhaps for a season or two until they see cash flow after which a proper concrete monk would be the best option. I'm still on the move at the moment and as such I don't have access to much of my printed literature. I'm sure I have allot more literature in South Africa which I could salvage at some point. I have AutoCAD drawings of concrete monks which I drew several years ago which I can locate and add to the list at a later date. The monk is still the most preferred method of level control, pond drainage and overflow protection on many commercial fish farms in South Africa and Europe. All the best Ramon M. Kourie ----- Original Message ----- *From:* Piers, ALR &lt;adrianp(a)sun.ac.za&gt; <mailto:adrianp@sun.ac.za%3E> *To:* sarnissa-african-aquaculture(a)lists.stir.ac.uk <mailto:sarnissa-african-aquaculture@lists.stir.ac.uk> *Sent:* Saturday, March 06, 2010 11:56 AM *Subject:* Re: [Sarnissa-african-aquaculture] monks and standpipes Dear Raymond, I would like to make a clarification here. A monk is not simply a means of draining ponds, it has a threefold function. 1. Level control 2. Pond drainage, and 3. Overflow protection The last being one of the most important. With the present rains here in Uganda it demonstrates my point. If pipes are used for drainage, a separate spillway still needs to be added to any well constructed pond. If the costs are added up, a pipe plus a spillway is invariably more expensive than a monk. Adrian Piers, African Fish Ltd. Newsletter Editor, Aquaculture Association of Southern Africa and Aquaculture Institute of South Africa Phone ++27 21 808 3712 Mobile ++27 (0) 73 264 4280 *From:* sarnissa-african-aquaculture-bounces(a)lists.stir.ac.uk [mailto:sarnissa-african-aquaculture-bounces@lists.stir.ac.uk] *On Behalf Of *Raymond Mwangata *Sent:* 06 March 2010 10:30 AM *To:* sarnissa-african-aquaculture(a)lists.stir.ac.uk *Subject:* Re: [Sarnissa-african-aquaculture] monks and standpipes thanks for your observation.but i would relate this to the cost of the two.most of the ponds am seeing in east Africa are semi intensive systems and are owned by small scale fish farmers at subsistence level.this therefore translates the fact that its cheaper to get a 2 meter PVC pipe as drainage structure compared to a monk which requires building materials and cost of labour which most farmers can not afford. regards, Raymond Ministry of fisheries development. Nakuru fisheries station Rifty valley region.Kenya. cell: +254722902914 Rwanda monks and comparison held. other the newly of the very expensive. for each compromised. I between ------------------------------------------------------------------------ Hotmail: Free, trusted and rich email service. Get it now. <https://signup.live.com/signup.aspx?id=60969> No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.435 / Virus Database: 271.1.1/2726 - Release Date: 03/06/10 07:39:00 ------------------------------------------------------------------------ _______________________________________________ Sarnissa-african-aquaculture mailing list Sarnissa-african-aquaculture(a)lists.stir.ac.uk http://lists.stir.ac.uk/cgi-bin/mailman/listinfo/sarnissa-african-aquacultu… ------------------------------------------------------------------------ _______________________________________________ Sarnissa-african-aquaculture mailing list Sarnissa-african-aquaculture(a)lists.stir.ac.uk http://lists.stir.ac.uk/cgi-bin/mailman/listinfo/sarnissa-african-aquacultu…