This study examines the possibility of supporting improved
\ncatchment irrigation management by evaluating scenarios based on sound
\nhydrological analysis using the Water Evaluation and Planning System (WEAP).
\nThe scenarios identify clear options and practical implications for irrigation
\nmanagement which can inform policymakers and relevant stakeholders. These
\nstakeholders include the Farmer Water User Communities (FWUCs), commune
\ncouncils (CCs), and the Provincial Departments of Water Resources and
\nMeteorology (PDOWRAM) who are currently in charge of irrigation management at
\ncommunity and provincial levels. Contemporary changes in farming practices in Stung Chrey Bak
\ncatchment form the background to this study. Rice farming is changing rapidly
\nfrom rain-fed mono-cropping to irrigated double or triple cropping. Seven
\nirrigation schemes have been built to extract water from the stream so that the
\nrice growing area of 10,367 ha (741 ha in the dry season) is no longer heavily
\ndependent on rainfall. Dry season rice is grown mainly in the downstream area
\nof the catchment where cultivation depends entirely on irrigated dry season
\nfarming because flooding during the wet season, and hence farmers here are
\nentirely depend on dry season stream flow. Water shortages have led to some
\nrice growing areas being damaged, and competition between water users in
\ndownstream irrigation schemes has been particularly intense in recent years, especially
\nin the months of February and March. The rapidly growing demand for irrigation has
\ncreated and intensified competition for water resources, raising concern about
\nthe equity of water allocation, sustainability of water usage, social friction
\namong water-user communities, and long term sustainability of water resources
\nand environmental impact of irrigation. In addition, traditional supply-based
\nwater planning is no longer appropriate. Instead, planning for water-supply
\nprojects should also focus on demand-side water management. Government policy reform, including river basin management, is
\nexpected to address some of these concerns. However, sound water management
\nrequires good knowledge and applicable tools to support well informed
\ndecision-making. The WEAP model incorporates the values of demand management into a
\npractical applicable water resource planning tool for: (1) defining modelling
\nproblems; (2) establishing the current account, from which different irrigation
\ndemand management scenarios can be evaluated; (3) simulating scenarios; and (4)
\nevaluating these scenarios against criteria such as water availability and
\nenvironmental in-stream flow (e-flow) conditions. Three demand management scenarios were developed for this study \u2013
\nreference, 5 percent annual increase in irrigation demand, and additional
\nreservoir storage from scheme numbered 5. E-flow demand was estimated to be 30
\npercent of monthly stream flow. The e-flow demand was not included in the
\ncurrent account (2007). However, it is included in the three scenarios. In 2007, stream flow was calculated at 289 million m3 and the
\nirrigated area was 10,367 ha. The lowest flow measured in the middle part of
\nStung Chrey Bak catchment was 4 million m3 in March, 5.6 million m3 in
\nFebruary, and 12.9 million m3 in June. The reference scenario simulation shows that this stream flow,
\nwithout allowing for e-flow, is sufficient for irrigating a dry season rice
\ngrowing area of 741 ha and wet season area of 9,626 ha. However, the
\ncatchment\u2019s water supply is not sufficient when the e-flow, water use by other
\nsectors, livestock, and small rural industrial consumption, which are not
\nincluded in this study, are taken into account. There is an unmet demand
\nof 4.2 million m3, mostly in June (0.95 million m3 in March). The 5 percent annual increase in irrigation demand simulation
\nshows that the irrigated area will have reached 16,083 ha by 2016. This would
\nhave two implications: (1) without considering e-flow, climate variability and
\nother water usages, unmet irrigation demand will be 2.97 million m3 mainly in
\nJune; (2) allowing for e-flow would increase unmet irrigation demand to 7.89
\nmillion m3, mostly in June (1.3 million m3 in March). The additional reservoir storage scenario simulation shows that
\nthe reservoir capacity in irrigation scheme numbered 5 is small and can barely
\nhelp improve unmet demand in times of drought. There are topographical and land
\nacquisition constraints that reservoir storage cannot be enlarged. Three patterns of stream flows were observed: dry season
\n(November-April), wet season 1 (May-July: low flow) and wet season 2
\n(August-October: high flow). The variations of stream flow have implicated
\ngreatly on farming and ecosystem; i.e. low stream flow in March and June limits
\nfarmers from increasing their irrigating areas, and it causes environment degradation.
\nThe conclusion is that when taking into account the e-flow demand the irrigated
\narea should be limited to 10,000 ha, including 740 ha in the dry season.
\nAlternatively, when the e-flow is considered as a secondary priority; the
\nirrigated area should not be expanded beyond 12,000 ha. <\/p>\n
In a situation of water limitation, a harmonising crop planning
\nbetween upstream and downstream cropping areas, bases on stream flow patterns,
\nis crucial in optimising the use of water resources in agriculture. The lowest
\nstream flow is in March. Water allocation between schemes numbered 5, 6, and 7
\nare critical because the irrigation demand in that month is peaked. Because the
\nstream flow decreases from December to March, cropping patterns in schemes numbered
\n6 can start in an early November and irrigation scheme numbered 7 can start in
\nmid or late November in order to avoid an overlapping of irrigation peak demand
\nperiod. <\/p>\n","protected":false},"excerpt":{"rendered":"
This study examines the possibility of supporting improved catchment irrigation management by evaluating scenarios based on sound hydrological analysis using the Water Evaluation and Planning System (WEAP). The scenarios identify clear options and practical implications for irrigation management which can inform policymakers and relevant stakeholders. These stakeholders include the Farmer Water User Communities (FWUCs), commune councils (CCs), and the Provincial Departments of Water Resources and Meteorology (PDOWRAM) who are currently in charge of irrigation management at community and provincial levels. […]<\/p>\n","protected":false},"featured_media":0,"template":"","meta":{"_acf_changed":false,"_kad_blocks_custom_css":"","_kad_blocks_head_custom_js":"","_kad_blocks_body_custom_js":"","_kad_blocks_footer_custom_js":"","site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[5],"tags":[],"class_list":["post-33107","publications","type-publications","status-publish","hentry","category-uncategorized"],"acf":[],"yoast_head":"\n