Report 19. Water harvesting and small-scale irrigation

Abstract

The objective of this consulting work was to develop recommendations for water harvesting systems development in the Northwest Region of Haiti for the BIG project and for livestock watering. The consultant also observed the currently used conservation measures from engineering viewpoints such as structure, strength, design and installation. The following interventions for water harvesting and soil/water conservation were observed in the three CARE regions: a. Biointensive Garden (BIG) projects. b. Rock wall check dams. c. Hedgerows. d. Roof runoff catchments. e. Roadside runoff catchments. f. Springs. g. Irrigation projects: head works and canals. h. A large scale hill-side runoff catchment system (approximately 30 m by 30 m) in Passe Catabois. Any water harvesting sytems (either from field or roof) in the Northwest region will offer various benefits: (1) water for irrigations, livestock, and other beneficial uses; (2) reducing runoff and erosion in ravines; and (3) recharging aquifers in the region. The first benefit will provide direct incentives to the BIG participants and others who build water harvesting systems and the other two will provide a long term benefit to the region and the country. The climate and landscape of the region seem to be adequate for water harvesting systems and demand for such water sources is high. It was observed that many villagers were interested in the BIG project. Success of the BIG project would rely on good water sources for irrigation and livestock as well as the participants' strong will. In general it is feasible to harvest water from roofs, roadsides, and hill slopes in the three regions visited during the consultancy. A roof catchment system is proposed for the Northwest Region. It is similar to the existing systems in the region but with a few modifications. In Bombardopolis and Passe Catabois regions, large scale community-based water harvesting systems (over 1,000 m[superscript]3 water holding capacity) could be developed should pond sites be available. Construction of water holding dams for irrigation in streams and rivers would be ineffective under the current severe sedimentation problems. Any large scale irrigation schemes in the area should be considered only after conservation measures show evidence of reduction of hill side erosion and lower sediment loads in the streams. Soil conservation and erosion control can be achieved by any field practices which reduce the erosive forces of runoff from hills and erodible field conditions. Overall the PLUS project seems to be working in the right direction and has been achieving its objective of conservation by mitigating erosion problems while providing incentives for the participating farmers. However, some problems and drawbacks exist in the gully control and the BIG component of the project. In the Northwest Region many ravines have been badly damaged by past erosion that it may not be feasible to protect the gullied areas from further expansion without implementing extensive conservation measures such as gabions or concrete structures. The efforts of the PLUS project would be more successful by further emphasizing the conservation measures on the primary source areas of erosion-causing runoff. Erosive forces of runoff would be reduced by controlling runoff from hill tops, hill sides, and newly developed shallow ravines. Gully-control check dams should be strengthened with rocks behind the vegetative plugs and hill sides protected with rock walls. Reduction of runoff is the first step to control most erosion problems and it should be done from the top of hills. It may take more areas to deal with than controlling runoff in gullies but it is technically less difficult. Any field practices and systems which reduce runoff and its concentration from hill tops and hill sides would reduce the erosion potential by reduced erosive forces of the runoff. Successful conservation measures will directly benefit the participants with better soil and more water retention and will also benefit the region and the country as a whole with reduced expansion of gullies, increased aquifer recharge, and less sediment loads in the valleys. Good maintenance of water harvesting systems is of utmost importance as well as design and construction of the systems. Proper compaction of pond soil can effectively seal pore spaces which results in reduced seepage losses. Seepage rates are further reduced with clay, ash, or animal manure which is spread on the pond bottom and mixed with the soil before compaction. Inspection and necessary maintenance should be done after major storm events. Maintenance should include: cleaning of sediments from sediment trap and pond, repairing of washed areas, and additional compaction should seepage increased. The following systems and practices are recommended for immediate or future implementation for improved performance and outcome of the BIG and PLUS projects. a. Field water-harvesting systems with ponds for multi-ownership BIG project such as one in Bombardopolis and roof-runoff catchment systems for single family ownership BIG projects. The water collected from roof catchment may be safely used for domestic purposes. Schematics of these structures are given in Appendices. Brief concept of the design was discusses with the personnel in the regional office. b. Training workshop on small scale irrigation and irrigation scheduling for the BIG project participants through training of regional office personnel. c. Installation of rock walls and hedgerows in shallow ravines and check dams in gullies. Design details of these structures are shown in Figures 1 and 2. Brief concept of the design was presented to the personnel in the regional office.

Objektif travay konsiltasyon sa-a se pou bay rekòmandasyon pou devlope sistèm pou ranmase dlo lapli nan Nòdwès peyi Dayiti pou fè jaden legim ak pou fè elvaj. Konsiltan-an t obsève tou mwayen ki itilize nan Pwojè-a pou kenbe tè ak dlo lapli. Kòm enjenyè, li gade si estrikti yo solid, si yo te byen chwazi, byen planifye, si yo te byen fèt. Nan twa (3) rejyon CARE ap travay, men ki teknik pou ranmase dlo lapli ak pou kenbe tè ak dlo konsiltan-an te observè: a. Jaden legim (BIG: jaden byoentansif) b. Mi sèk nan ravinn c. Ranp vivan d. Dal pou ranmase dlo lapli e. Dren-kanal bò rout f. Sous g. Estrikti irigasyon: baraj nan tèt sitèm nan ak kanal yo h. Yon gwo sistèm (30 mèt pa 30 mèt konsa) pou kapte dlo lapli nan Paskatabwa. Nenpòt ki sistèm pou ranmase dlo lapli (sou tè yo oubyen sou tèt kay) ki fèt nan Nòdwès-la ap genyen pliziè avantaj: (1) ap genyen dlo pou aroze plant, pou bèt, k-ap sèvi pou lòt bagay ankò; (2) dlo k-ap desann ak erozyon nan ravinn ap diminye; (3) ap genyen plis dlo anba tè nan rejyon-an. Premye pwen-an se yon avantaj dirèk pou moun k-ap fè jaden legim yo. Lòt de pwen yo se yon avantaj alontèm pou rejyon-an ak peyi-a. Klima ak peyizaj rejyon Nòdwès-la sanble ta favorab pou etabli sistèm pou ranmase dlo lapli. Genyen anpil demand pou dlo. Sanble tou anpil moun enterese nan jaden legim. Pou gen siksè nan fè jaden legim non sèlman fòk patisipan yo gen bòn volonte men fòk yo jwenn dlo pou aroze jaden-an ak pou bay bèt. Anjeneral li posib pou ranmase dlo ki soti sou dal kay, bò rout, ak sou mòn nan tou le twa rejyon konsiltan-an te vizite. Konsiltan-an pwopoze yon sistèm ranmase dlo sou dal pou rejyon Nòdwès-la. Se menm sistèm ki egziste deja-a ak kèk ti chanjman. Nan zòn Bongadopolis ak Paskatabwa, se posib pou fouye gwo basen pou ranmase dlo lapli pou sève kominote-a (yon sistèm ki ka kenbe apeprè 1.000 mèt kib dlo). Li pa rekòmande pou konstwi baraj irigasyon sou rivyè akòz gwo pwoblèm debri (sedimen) ewozyon charye soti nan mòn yo. Tout gwo sistèm irigasyon nan zòn nan to dwe fèt sèlman lè yo fin pwoteje mòn yo kont ewozyon, lè gen mwens sedimen ki vinn tonbe nan rivyè yo. Kontwò ewizton ak konsèvasyon sòl kapab fèt ak nenpòt ki teknik ki ka diminye fòs dlo k-ap desann nan mòn yo e ki anpeche tè-a ale fasil. Anjeneral, Pwojè PLUS sanble ap travay nan bon direksyon-an e sanble ka reyalize objektif konsèvasyon li yo paske nan chèche rezoud pwoblèm ewozyon yo li konsidere avantaj ekonomik pou patisipan yo. Sepandan, genyen kèk pwoblèm ki egziste nan kontwòl ravinn ak nan jaden legim yo. Nan rejyon Nòdwès-la ewozyon si tèlman finn ravaje anpil ravinn, pou anpeche yo vinn pi mal se teknik tankou gabyon oubyen beton ki ta valab. Efò Pwojè PLUS ap fè t-ap gen plis siksè si yo ta kontwole ewozyon-an depi kote li kòmanse. Fòs dlo-a ta diminye depi nan tèt mòn yo, sou mòn yo ak nan ravinn ki fèk fòme yo ki poko twò fon. Mi sèk nan ravinn yo ta dwe ranfòse ak wòch dèyè baraj ki fèt ak bwa ak plant yo, e mòn yo ta dwe pwoteje ak kòdon wòch. Diminye fòs dlo-a se premye pa nan kontwole pwoblèm ewozyon e li ta dwe fèt depi nan tèt mòn yo. Sa ta mande pou Pwojè-a travay sou plis tè pase travay kontwole fòs dlo nan ravinn sèlman, men teknikman li mwen difisil. Nenpòt ki teknik ak sistèm ki diminye kantite ak konsantrasyon dlo k-ap desann soti nan mòn yo ap diminye posiblite pou genyen ewozyon paske fòs dlo-a diminye. Bon teknik konsèvasyon yo ap pote avantaj dirèk pou patisipan yo paske bon tè ak plis dlo ap rete nan jaden yo. Rejyon-an ak peyi-a ap benefisye tou paske ravinn ap sispann laji, ap genyen plis dlo anba tè, ap genyen mwens sediman ki desann nan bafon yo. Li trè enpòtan pou fè bon jan antretyen sistèm pou ranmase dlo lapli yo, menmjan li enpòtan pou byen planifye ak konstwi yo. Fòk tè basen yo byen foule pou bouche tout twou pou dlo-a pa rantre nan tè. Vitès dlo-a ap rantre nan tè (enfiltrasyon) ka diminye ak ajil, sann, oubyen fimye melanje ak tè nan fon basen-an avan li foule. Enspeksyon ak entretyen te dwe fèt chak fwa yon gwo lapli finn tonbe. Men ki sa ki ta dwe fèt nan entretyan-an: netwaye basen-an pou retire sediman yo, repare kote dlo-a andomaje, foule tè-a kote dlo-a ap rantre nan tè. Men sistèm ak teknik ki rekòmade pou kounye-a ak pi devan pou ede rezoud pwoblèm dlo pou jaden legim (BIG) ak lòt aktivate Pwojè-a: a. Sistèm basen pou ranmase dlo lapli pou aroze jaden legim (BIG) ki pou pliziè moun ak sistèm ranmase dlo sou dal kay pou aroze jaden legim ki pou yon sèl fanmi. Dlo ki ranmase sou dal kay yo kapab sèvi san pwoblèm pou bezwen moun nan kay-la. Chema estrikt sa yo prezante nan anèks dokiman sa-a. Diskisyon te fèt ak pèsonèl rejyon yo pou planifye estrikt sa yo. b. Seminè fòmasyon sou ti sistèm irigasyon ak pou moun yo konnen ki lè pou aroze, ta dwe fèt nan sant fòmasyon rejyon yo ak moun ki genyen jaden legim (BIG) yo. c. Konstwi kòden wòch ak ranp vivan nan ravinn ki pa twò gwo ak mi sèk (sèy) nan pi gwo ravinn yo. Detay estrikt sa yo bay nan figi 1 ak 2 nan dokiman-an. Konsiltan-an te prezante bay pèsonèl biwo rejyon yo jan li panse estrikt sa yo ta dwe fèt.