{"id":117008,"date":"2021-08-11T17:35:50","date_gmt":"2021-08-12T00:35:50","guid":{"rendered":"http:\/\/www.lankaweb.com\/news\/items\/?p=117008"},"modified":"2021-08-11T17:35:50","modified_gmt":"2021-08-12T00:35:50","slug":"partitioning-water-between-agriculture-and-hydro-power-to-maximize-sri-lankas-clean-energy-output","status":"publish","type":"post","link":"https:\/\/www.lankaweb.com\/news\/items\/2021\/08\/11\/partitioning-water-between-agriculture-and-hydro-power-to-maximize-sri-lankas-clean-energy-output\/","title":{"rendered":"Partitioning water between agriculture and hydro-power to maximize Sri Lanka’s clean energy output."},"content":{"rendered":"

By Chandre Dharmawardana.<\/em><\/span>
National Research Council of Canada, Ottawa and Department of Physics and Astronomy Universit\u00e9 de Montreal. <\/em><\/span><\/h2>\n\n\n

The largest drain on Sri Lanka’s foreign exchange earnings is in purchasing\u00a0 fossil fuels for power and transport,\u00a0 and in feeding\u00a0 the 22 million people who depend on a mere million hectares of arable land, as compared to 44 million hectares\u00a0 in Canada with a population of just 37 million. Much of agricultural land\u00a0 in the dry zone\u201d\u00a0 depends on irrigation water. This\u00a0 is provided by a network of reservoirs that tap the heavy rains of the hill country to deliver the water to the agricultural regions via rivers and irrigation canals. \u00a0<\/p>\n\n\n\n

In  previous articles (e.g.,\nIsland 7-Aug-2021, Island: https:\/\/island.lk\/clean-energy-without-foreign-exchange\/<\/a>;\nColombo Telegraph: https:\/\/www.colombotelegraph.com\/index.php\/clean-practical-solutions-to-sri-lankas-energy-crisis\/<\/a>) \nI had restated what I had stated in many articles extending back into two\ndecades, namely, that just by CUTTING DOWN EVAPORATION  from our\nhydro-electric tanks, we can boost our clean energy production to such an\nextent that the targets of 70% production of clean energy become \ncompletely  possible. <\/p>\n\n\n\n

Here I point out the possibility\nof  boosting power production EVEN FURTHER by optimal partitioning of\nwater<\/strong> between agriculture and hydro-power production, by shielding the\nwater in the IRRIGATION tanks from EVAPORATION, and in NOT USING WATER to\ncontrol weeds in paddy fields.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

\u00a0\u00a0 \u00a0
Figure 1.\u00a0 Schematic of the main Mahaweli hydro-power and agricultural irrigation network.

In ancient times, small manually built tanks (weva\u201d) supplied water to small hamlets (gama\u201d) where people lived at a precarious subsistence level (see Prof. Siriweera’ study of ancient food security).\u00a0 The\u00a0 temple or Kovil was the only spiritual, cultural and educational resource. That ancient hydraulic system held pride of place in the ancient world. But it did not tap the heavy rainfall of the hill country.\u00a0 The total population\u00a0 sustained by the whole Land even at its best times was probably less than today’s population in\u00a0 Colombo.

In contrast, today’s hydraulic system not only provides irrigation water, but also electric power that drives modern technologies, hospitals, electrified transport, and every aspect of daily life at levels of culture and leisure that were not available even to elites of the ancient world.

The attached figure (Figure 1, credits: Thushara de Silva et al., 2019, Vandebilt\u00a0 University, USA) shows how hydro-power stations (red squares) of the Mahaweli system are also\u00a0 associated with the various irrigation schemes (green hexagons)\u00a0 denoted by\u00a0 A, B, C, \u2026 H, MH etc.\u00a0 The head water of the Mahaweli is diverted at Pollgolla towards the north\u201d via Bowatenna mainly for agriculture, while another branch supplies the Minipe agricultural regions via Randenigala and Rantambe power stations.<\/p>\n\n\n\n

However, if more water is sent to\nirrigated agriculture, there is less available for power production.\nAgriculture needs water in large amounts at specific times, while power\nproduction uses water far more steadily. The water that is used for hydro can\nbe used in agriculture when stored downstream and released at the required\ntime. <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Figure 2.  Agricultural water\nrequirements in various Mahaweli Systems in millions of metric tons per\nhectare.  [Credits: Thushara de Silva et al.,<\/p>\n\n\n\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Vanderbilt University, USA, 2019]<\/p>\n\n\n\n

Figure 2 shows the monthly water\nuse  in the two planting seasons. The upstream reservoirs have to provide\nenough water to the irrigation reservoirs at a time to be  ready to supply\nthe irrigation water as soon as needed.  I find that it quite sufficient\nto model the water-requirement by a sum of just two Gaussians. Similar simplifications\ncan be done, when analytic calculations can be carried out as the differential\nequations become quite tractable. Such analytic models enable one to establish\nmore reliable asymptotic behaviour of these systems, and determine upper and\nlower bounds to the critical indices and carry out critical path anlayses and\nother evaluations far more conveniently than with purely numerical\n“brute-force” computer simulations popular with Engineers and those\nwho write glossy “proposals”. <\/p>\n\n\n\n

More importantly, exploring such\nanalytic models mathematically  enables one to obtain an intuitive\nphysical familiarity with the system.  We find that water requirement can\nbe cut down by beyond a FATOR OF TWO implementing two simple provisions:<\/p>\n\n\n\n

(A) the irrigation tanks are covered by floats to prevent evaporation. This also prevents algae and water weeds, and improves the aquatic environment. The floats may also carry solar cells and connected to the central grid using smart switching technologies that are now standard, even in small islands like Hawaii. So if the CEB claims that Sri Lanka’s power grid is “too small” to handle power fluctuations easily or introduce smart grid approaches, such a claim is simply not valid.

(B) WATER IS NOT USED for weed control in paddy planting. \u00a0<\/p>\n\n\n\n

Instead, weeds should be controlled\nusing safe herbicides like glyphosate.  There is of course socio-political\nresistance to “chemicals” entrenched in occult beliefs in\nrevelations by God Natha\u201d, or due to baseless propaganda against agro-chemicals\u201d. \nTo meet that challenge, the  so-called System Rice Intensification\u201d (SRI)\nmethods  may be used. <\/p>\n\n\n\n

SRI has been tested out in India and\nMadagascar.  It  is said to increase yields by over 30%, i,e., \n4-5  tonnes per hectare instead of at most three tonnes per hectare\nobtained with reduced use of chemical\u201d fertilizers, while also using 40% LESS\nwater than conventional methods. If chemical fertilizers and humus are used\ntogether, the yields become 8-10 tonnes per hectare, with even less soil erosion.\nHowever, a pilot project  to test a new idea is needed before extensive\nadoption.<\/p>\n\n\n\n

The steps (A) and (B) or similar ideas are not included in the usual studies on optimizing water management in multipurpose reservoir\u00a0 systems even though quite complex models like RIBASIM, WEAP (e.g., see,\u00a0 Louckes and van Beek 2017) etc., have been used\u00a0 by engineering researchers. Such models, though complex, are only as good as the ideas incorporated into them. Ideas can be tested more transparently using simpler analytic models of the sort used in theoretical physics. There are also losses in seepage that are not included in standard engineering models, or in my calculations, as no simple engineering approach is currently available to reduce seepage from the bottom of the reservoirs.<\/p>\n\n\n\n

All this suggests  that if\nreservoir capacity permits, the water available for hydroelectricity can be\neasily doubled while providing more than adequate irrigation water to the\nagricultural schemes of  Lanka and providing ALL THE NEED POWER using only\nhydro power, for at least the next decade. If so  much water can be saved,\nit makes good sense to expand reservoir capacity or bring into service the\nabandoned small tanks that are found in many parts of the dry zone \u2013 but they\ntoo will need evaporation shields. Furthermore, the possibility of raising the\nKothmale dam to increase capacity by 20% has been proposed by Engineer\nKenderagama (5-Nov-2020, Island newspaper). If this is in fact  feasible,\nthe hydro-power output will also increase by almost 20%. Thus we see that \nlack of a power research Institute\u201d similar to, say, the TRI for the eta\nsector, hampers in the evaluation and analysis of new ideas in such a vital\nnational endevour like power production, as the CEB alone is not equipped to\ndeal with such matters.<\/p>\n\n\n\n

Kendaragama has also drawn attention\nto the question of the long-term safety of the hydro-power dams.<\/p>\n\n\n\n

The projections of power needed by Sri Lanka given by the CEB are INCORRECT and are a gross under-estimate as the CEB does not seem to have considered that most motor vehicles will use electric power within a decade.<\/p>\n\n\n\n

In any case, the proposed steps are\na means of establishing a solid shield against global warming and persistent\ndrought that will be part of the future weather patterns. Then the mechanisms\nput in to prevent evaporation or deal with sudden excess water will\nbecome  God Sent\u201d provisions. <\/p>\n\n\n\n

The technology that is needed for\nthe main proposal made here to save water, i.e.,  by introducing floating\nevaporation shields on reservoirs,  does not need modern technology or\n“foreign exchange”. Adding solar cells on to the floats, and using\nsmart grid switching technology of course will bring us to the 21st century\ntechniques, but at very little cost.<\/p>\n\n\n\n

By Chandre Dharmawardana.
National Research Council of Canada, Ottawa and Department of Physics and Astronomy Universit\u00e9 de Montreal. <\/p>\n","protected":false},"excerpt":{"rendered":"

By Chandre Dharmawardana.National Research Council of Canada, Ottawa and Department of Physics and Astronomy Universit\u00e9 de Montreal. The largest drain on Sri Lanka’s foreign exchange earnings is in purchasing\u00a0 fossil fuels for power and transport,\u00a0 and in feeding\u00a0 the 22 million people who depend on a mere million hectares of arable land, as compared to […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":true,"template":"","format":"standard","meta":{"footnotes":""},"categories":[85],"tags":[],"class_list":["post-117008","post","type-post","status-publish","format-standard","hentry","category-chandre-dharmawardana"],"_links":{"self":[{"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/posts\/117008","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/comments?post=117008"}],"version-history":[{"count":0,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/posts\/117008\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/media?parent=117008"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/categories?post=117008"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/tags?post=117008"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}