{"created":"2022-01-27T02:41:53.706601+00:00","id":2002888,"links":{},"metadata":{"_buckets":{"deposit":"c1c99f64-1f06-486c-865c-7b15b23d96cf"},"_deposit":{"id":"2002888","owners":[1],"pid":{"revision_id":0,"type":"depid","value":"2002888"},"status":"published"},"_oai":{"id":"oai:u-ryukyu.repo.nii.ac.jp:02002888","sets":["1642837622505:1642837905044:1642837917016","1642838403551:1642838407312"]},"author_link":[],"item_1617186331708":{"attribute_name":"Title","attribute_value_mlt":[{"subitem_1551255647225":"沖縄水利の実態分析と畑地灌漑に向けての小規模水利開発に関する研究(農業工学科)","subitem_1551255648112":"ja"},{"subitem_1551255647225":"A Study on Present Status of Agricultural Water Use and Small Scal Development of Agricultural Water for Upland Irrigation in Okinawa (Department of Agricultural Engineering)","subitem_1551255648112":"en"}]},"item_1617186419668":{"attribute_name":"Creator","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"吉永, 安俊","creatorNameLang":"ja"}]},{"creatorNames":[{"creatorName":"Yoshinaga, Anshun","creatorNameLang":"en"}]}]},"item_1617186476635":{"attribute_name":"Access Rights","attribute_value_mlt":[{"subitem_1522299639480":"open access","subitem_1600958577026":"http://purl.org/coar/access_right/c_abf2"}]},"item_1617186626617":{"attribute_name":"Description","attribute_value_mlt":[{"subitem_description":"沖縄の水利開発に社会資本が投入されるのは昭和初期からである。史書に残る水利開発は個人,村(現在の字に相当)による数百m^3程度の溜池や,小川に堰をつくり数百mの水路を引く程度のものであり,きわめて小規模であった。琉球王府による水利開発は皆無であり,土木のような幕府や藩主による水利開発は沖縄ではみられない。昭和初期から行われた農業用ダムによる水利開発は,これまでに65ダム(総貯水量1,200万m^3)造られた。しかし約6割が10万 m^3以下のダム容量であり,また,集水面積は半数以上が0.5m^3以下の小規模ダムである。ダム規模のこのような零細性は島嶼からなる地形的要因も原因するが,圃場団地の小規模分散性にも原因がある。つまり,それぞれの団地が独自の小規模水利開発を行ったためである。現在の水利開発は,生活用水との競合が激しくきわめて厳しい状況にある。沖縄本島の唯一の水源地帯である北部山岳地域においては,生活用水,工業用水専用の国管理の5ダムが造られ,さらに 9ダムの計画が進められている。また9河川からは県が,生活用水として取水しており,北部山岳地帯においては農業用水開発の余地がほとんどない状態である。この地域においては,遠距離導水に頼る水資源逼迫地域のための水利開発はきわめて困難な状況にある。したがって,沖縄本島中南部や珊瑚石灰岩からなる水資源逼迫地域は,独自の水利開発の必要性にせまられている。本研究はこの様な地域における水資源開発として,小規模貯水池による畑地帯の地表水開発に着目して,それの有効性と小規模貯水池のシステム特性を明らかにした。また,貯水池の容量決定には畑地帯の地表流出量を知る必要があり,そのために,沖縄の主要土壌である国頭マージ(名護),ジャーガル(西原),島尻マージ地帯(宮古島)において2&acd;5年間の水文観測を行って,雨量と流出率の関係を明らかにした。両者の関係を,営農行為に伴う畑地流域の不安定性を考慮し,川上の経験式で表示した。経験式の定数は最小自乗法で求めた。これによって初めて沖縄の主要土壌地帯の流出率と降雨の関係が明らかになった。3土壌地帯の関係を(6-1)&acd;(6-3)式に示す。国頭マージ : f=1-3.14/R^<0.456>……(6-1) ジャーガル : f=1-3.34/R^<0.424>……(6-2) 島尻マージ : f=1-2.10/R^<0.231>……(6-3)","subitem_description_type":"Other"},{"subitem_description":"これらの実測流出率をもとに,これまで沖縄における小規模貯水池に用いられてきた計画流出率を検討した。各地における計画流出率は,日雨量の60mm以下の雨量域ではすべてが実測値より大きい値であることがわかった。これは60mm以下の降雨による雨量割合が年雨量の70%に達すること,および数千 m^3&acd;数万m^3m^3の小規模貯水池であることを考慮すれば,過大な計画流出率である。つまり小規模貯水池は降雨頻度の多い小雨域の影響を大きく受けるからである。したがって,ほとんどの貯水池容量は過小に計画されている。小規模貯水池による畑地帯における地表水開発について,潅漑面積,集水面積,貯水池容量の相互関係をシミュレーションにより明らかにした。単位面積を潅漑するために必要な集水面積と貯水容量は(6-4)式で示される双曲線の関係になる。A=α/(V-β)^n……(6-4) ここでAは集水面積(ha),Vは貯水池容量(m^3),7,α,nは定数,βは最小貯水池容量(m^3)である。(4)式を用いれば任意の集水面積における貯水池容量を直ちに求めることができる。なお,両者の関係は10年確率値におけるものである。(4)式における最小貯水容量は集水面積を無限大に拡張しても,用水不足水量が発生する容量で,これは貯水池における無流入期間の最大取水量に等しい。つまりこれ以上,貯水容量を小さくすれば,10年に1年の用水不足発生は許容するという条件が崩れ,計画が成立しなくなる。この最小貯水池容量は貯水池計画における下限界容量である。式(4)における貯水池容量と集水面積の関係は降雨特性,潅漑特性,流出特性の影響を受ける。一般的に降雨量が多く,流出率の高い地域では,同一集水面積における貯水池容量は小規模化する。節水潅漑は大幅な貯水池容量縮小が可能となる。特に,集水面積が小さく,貯水池容量を大きくとらなければならないような地域においては,節水灌漑による貯水池容量縮小効果は大きい。また,客土や圃場整備事業等にともなう流出率増大も貯水池容量の規模縮小効果は大きい。貯水池が他の水源から用水補給が受けられる場合,大幅な貯水池容量の縮小が可能である。常時補給,条件補給いずれの場合も,それぞれの集水面積,補給開始時点において最も効率のよい (単位補給量による貯水池容量縮小量)補給水量が存在する。小規模貯水池のこの様な特性を踏まえた,貯水池計画はより効率的な水利開発を可能とする。なお,この貯水池による小規模水利開発は,沖縄の多くの水資源逼迫地域で天水依存農業からの脱皮を可能とする。","subitem_description_type":"Other"},{"subitem_description":"1. Objectives Okinawa prefecture consists of many small islands, of which size and relief are restrictive to hold sufficient water resources in general. Agricultural water tends to be deficient particularly in the areas of coral limestone and of Jahgaru in the central to southern parts of Okinawa Island. No rivers are formed in the coral limestone area because the soil derived there is quite permeable. Although there is such an exceptional case as Miyako Island where groundwater is conserved in the aquifer to some extent, water development for agricultural use is limited in most of the islands, because in the small island condition the sea water easily invades to the groundwater and furthermore, there occurs competition between the water uses for agriculture and daily life. On the other hand, the Jahgaru area extends to suburban of the central to southern cities, and where the development of agricultural water by constructing dam is not possible from the view point of geomorphology and land use. There is no groundwater in the Jahgaru area and even the water in small rivers, which are rather few in number with less volume of water, are contaminated with drains from households and not suited for agricultural use. Consequently, agricultural water is developed to the least extent in this area at present. However, there is a strong needs to have agricultural water developed, because the Jahgaru area occupies a good position for suburban agriculture coupled with relatively fertile soils. From economic point of view, investment for long distance transportation of agricultural water is regarded difficult in the present status of agriculture, since these areas of coral limestone and Jahgaru are located far away from available water resources. Consequently, agricultural water must be developed in the respective areas of coral limestone and Jahgaru. Small scale development of agricultural water, which is done by collecting surface run-off from the upland area to small reservoirs when it rains, is considered most economic and effective in order to meet the necessity as stated above. Agricultural water development in this way is also applicable to the dispersedly built greenhouses which tend to increase rapidly nowadays. Furthermore, small scale development is easily done by individual or a small group of farmers and considered best suited especially for Okinawan farmers who historically have not experienced in using and managing agricultural water by a large group.","subitem_description_type":"Other"},{"subitem_description":"In the present study, it was aimed to investigate the effectiveness of small scale development of agricultural water in Okinawa. In addition, discharge of the upland area was analyzed, a system of the small scale reservoir was analyzed on the basis of the discharge analysis and its characteristic was clarified. 2. Historical background on the small size of agricultural water development and cultivated lands Social investment started to develop agricultural water early in the Showa era, which started from 1926,in Okinawa. Before the Showa era, reservoirs of several hundred cubic meters and weirs in small streams were built by individual farmers or by Mura that was equivalent to present day Aza (a sub-unit of village) and digged canals from them extended only several hundred meters according to the recorded history. Agricultural water was developed in a large scale by the Shogunate Government and the feudal lord in many places of mainland Japan, but none was developed by the Ryukyu Dynasty in Okinawa. Sixty five dams have been built for agricultural use in Okinawa since the early Showa era, in which a total of the water reserve capacity are 12 million cubic meters. About 60% of the dams are below 0.1 million cubic meters in the respective capacity, and the respective watershed areas are less than 0.5 square kilometers in more than half of the dams. Such a small scale in the dam construction resulted from dispersal of the cultivated lands in addition to the geomorphology of the is","subitem_description_type":"Other"},{"subitem_description":"紀要論文","subitem_description_type":"Other"}]},"item_1617186643794":{"attribute_name":"Publisher","attribute_value_mlt":[{"subitem_1522300295150":"ja","subitem_1522300316516":"琉球大学農学部"}]},"item_1617186702042":{"attribute_name":"Language","attribute_value_mlt":[{"subitem_1551255818386":"jpn"}]},"item_1617186783814":{"attribute_name":"Identifier","attribute_value_mlt":[{"subitem_identifier_type":"HDL","subitem_identifier_uri":"http://hdl.handle.net/20.500.12000/3859"}]},"item_1617186920753":{"attribute_name":"Source Identifier","attribute_value_mlt":[{"subitem_1522646500366":"ISSN","subitem_1522646572813":"0370-4246"},{"subitem_1522646500366":"NCID","subitem_1522646572813":"AN00250548"}]},"item_1617186941041":{"attribute_name":"Source Title","attribute_value_mlt":[{"subitem_1522650068558":"ja","subitem_1522650091861":"琉球大学農学部学術報告"},{"subitem_1522650068558":"en","subitem_1522650091861":"The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus"}]},"item_1617187056579":{"attribute_name":"Bibliographic Information","attribute_value_mlt":[{"bibliographicIssueDates":{"bibliographicIssueDate":"1990-12-05","bibliographicIssueDateType":"Issued"},"bibliographicIssueNumber":"37","bibliographicPageEnd":"170","bibliographicPageStart":"49"}]},"item_1617258105262":{"attribute_name":"Resource Type","attribute_value_mlt":[{"resourcetype":"departmental bulletin paper","resourceuri":"http://purl.org/coar/resource_type/c_6501"}]},"item_1617265215918":{"attribute_name":"Version Type","attribute_value_mlt":[{"subitem_1522305645492":"VoR","subitem_1600292170262":"http://purl.org/coar/version/c_970fb48d4fbd8a85"}]},"item_1617605131499":{"attribute_name":"File","attribute_type":"file","attribute_value_mlt":[{"accessrole":"open_access","filename":"KJ00000161639.pdf","mimetype":"application/pdf","url":{"objectType":"fulltext","url":"https://u-ryukyu.repo.nii.ac.jp/record/2002888/files/KJ00000161639.pdf"},"version_id":"a3ab3de3-a7c8-4e00-acd2-f3b730631939"}]},"item_title":"沖縄水利の実態分析と畑地灌漑に向けての小規模水利開発に関する研究(農業工学科)","item_type_id":"15","owner":"1","path":["1642837917016","1642838407312"],"pubdate":{"attribute_name":"PubDate","attribute_value":"2008-02-14"},"publish_date":"2008-02-14","publish_status":"0","recid":"2002888","relation_version_is_last":true,"title":["沖縄水利の実態分析と畑地灌漑に向けての小規模水利開発に関する研究(農業工学科)"],"weko_creator_id":"1","weko_shared_id":-1},"updated":"2022-10-31T01:11:02.036017+00:00"}