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Agricultural Water Use in Lake Urmia Basin, Iran : An Approach to Adaptive Policies and Transition to Sustainable Irrigation Water UseFaramarzi, Nahal January 2012 (has links)
The Lake Urmia positioned in a closed basin in north-west Iran, positioned at altitude 1250 m above the sea level, and has been rapidly drying since 1990. The lake water level has declined to 1271.58 m in 2008 from the last highest record 1277.80 m in 1994. The lake water volume has fluctuated during the observation period and shows a drop from of 32 to 14.5 million cubic meters, while the lake salinity has increased from 205 to 338 g/l due to the evaporation and water inflow reduction. In the Lake Urmia basin, there has been an increase in public awareness of the possible environmental threat and the unpleasant socio-economical consequences on the region’s inhabitants. The main aim of this study is to assess the current water use pattern in the Urmia Lake basin system with emphasis on the agricultural sub-system, and to propose adaptive measures and sustainable water management scenarios. The study shows that the main cause for these changes are the diversion of rivers and streams for agricultural irrigation; agriculture is a sector with one of the highest water demands, and frequent drought in early 2000s exacerbated the situation. In addition, a growing population and the increased development of agricultural land has led to an increase in unsustainable practices which have an unpredictable impact on the Lake Urmia ecosystem. This study investigates sustainable water use strategies for Lake Urmia basin, and considers economic and environmental factors, including the loss of valuable ecosystems that highlights social and ethical issues for the current and coming generations.
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Why is collective participation not progressing in irrigation water management systems in India today? : case study Distributary 54 in Tungabhadra River Project, Karnataka, India /Simonsen, Mai. January 2008 (has links) (PDF)
Master's thesis. / Format: PDF. Bibl.
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Vulnerability of a Run-of-River Irrigation Scheme to Extreme Hydrological Conditions - A Case Study of the Bwanje Valley Irrigation Scheme, MalawiJohnstone, James 15 September 2011 (has links)
Irrigation plays an extremely important role in agriculture but climate change is predicted to modify climate patterns with potentially devastating consequences for irrigation. Potential impacts and adaptations are known, but not how implementation strategies may be implemented at the individual irrigation scheme level.
Using a case study approach and qualitative research methods this thesis describes the Bwanje Valley Irrigation Scheme (BVIS), Malawi in order to explain how water is managed. Subsequently, historical adaptations are described in order to draw conclusions concerning the vulnerability of the BVIS under normal and extreme hydrological conditions.
The BVIS is vulnerable in all conditions because it utilizes a common pool resource. As water supply decreases, irrigation water management becomes less and less equitable which makes the system extremely sensitive to changes in water supply. Capacity to adapt to climate change is limited to funding provided by external agencies which currently limit adaptations to reactive changes
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Institutions and “Collective Action” in a transitional country context : managing water resources in the Syr Darya River BasinFuleki, Blanka 08 1900 (has links)
À la suite de l'effondrement de l'Union soviétique, les états nouvellement formés de l'Asie centrale ont entrepris, à différents niveaux, des réformes de leurs secteurs agraires. Du point de vue de l'utilisation de l'eau d'irrigation, les réformes consistent notamment en des changements aux régimes fonciers et dans la décentralisation de la gestion du système de drainage et d'irrigation.
La plupart des institutions qui, durant l'époque soviétique, géraient le système d'irrigation et de drainage ont été abolies. Cela a créé un vide institutionnel et permis le développement d’institutions au niveau local qui puissent être participatives et appartenir aux utilisateurs. Pourtant, le contexte historique et contemporain de la région pose des défis particuliers pouvant nuire à un tel développement.
Les associations d'utilisateurs d'eau ou le gouvernement local gèrent l'irrigation et les systèmes de drainage au niveau local. Ces associations représentent souvent des initiatives conduites par les donateurs internationaux. Parallèlement, les institutions informelles et les modes traditionnels de coopération qui ont survécu à l'ère soviétique deviennent importants et quelques institutions créées durant cette ère demeurent toujours pertinentes.
Cette recherche consiste à évaluer le rôle d’action collective dans un système de gestion d’irrigation et de drainage dans le bassin versant de la rivière Syr-Darya dans un contexte changeant concernant les droits d’usage de l'eau et de la terre. L'étude cherche à
(1) saisir l'importance de l'eau d’irrigation dans les moyens de subsistance des utilisateurs dans la région de recherche;
(2) explorer certaines caractéristiques des institutions formelles et informelles à travers lesquelles les fermiers dirigent des systèmes de drainage et d’irrigation; et
(3) identifier les institutions qui appuient l'action collective et celles qui entravant son développement.
La méthodologie de recherche repose une revue bibliographique et sur un travail de terrain dans la vallée de Ferghana, au Kirghizistan, entre le 30 avril et le 31 juillet 2008. Les résultats de la recherche sont présentés comme une étude de cas. / Following the collapse of the Soviet Union, the newly independent countries of Central Asia undertook reforms of their agrarian sectors with varying degrees of speed and depth. In general, the reforms consisted of changes in the nature of land tenure and in the decentralization of irrigation and drainage management.
Through these reforms, former state management institutions were abolished leaving an institutional vacuum that presented an opportunity for the development of local-level management institutions. However, the historical context of the region poses particular challenges that may impede users to capitalize on such opportunities.
Water User’s Associations or the local administration manage irrigation and drainage systems at the local level. Water User Associations represent international donor-driven initiatives to introduce equitable, democratic and participative institutions for irrigation and drainage management. There are indications that those informal institutions and traditional modes of cooperation that survived the Soviet era are gaining importance.
This study maps out the various institutions, defined as "rules in use", that farmers employ to manage the irrigation and drainage system in the Ferghana Valley within the context of changing land and water rights. The key objectives of the study are (1) to understand the importance of irrigated water for local livelihoods in the research area; (2) to explore certain characteristics of the formal and informal institutions through which farmers manage irrigation and drainage systems; and (3) to depict ways in which “collective action” in irrigation water management can be strengthened.
The methodology consists of a synthesis of existing literature and fieldwork in the Ferghana Valley in Kyrgyzstan, from April 30 until 31 July, 2008. The results of the research are presented as a case study.
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Diseño de esquema de seguros agrícolas para mitigación del riesgo de sequías hidrológicas mediante modelos hidroeconómicos a escala de cuencaValenzuela Mahecha, Miguel Angel 16 October 2023 (has links)
[ES] La escasez de agua es un problema cada vez más recurrente para la agricultura de regadío en las regiones mediterráneas, siendo la sequía hidrológica uno de los problemas que afecta la disponibilidad de agua. Por lo tanto, es necesario establecer alternativas técnicas y económico-financieras que permitan a los regantes enfrentar este problema desde una visión amplia de la gestión del agua para uso agrícola a nivel de cuenca. Estas alternativas deben incluir instrumentos de planificación hidrológica, que permitan analizar el impacto de la sequía y determinar las medidas a implementar cuando el recurso hídrico disponible no sea suficiente para satisfacer las demandas de agua.
Uno de los instrumentos económicos y financieros para la gestión del riesgo agroclimático que se ha implementado con éxito y que cada día cobra más fuerza es el de los seguros agrícolas, más específicamente, el seguro indexado. Esta investigación pretende contribuir a mitigar el impacto de la escasez de agua en comunidades de regantes situadas en cuencas altamente reguladas, como el sistema de explotación del río Júcar, mediante el diseño de un nuevo esquema de seguro indexado por sequía hidrológica, basado en índices totalmente alineados con los procedimientos de gestión de la sequía a nivel de cuenca.
El proceso de diseño del seguro comprende 3 etapas. En la primera se evalúa económicamente el impacto de la sequía para establecer una indemnización unitaria, elemento base para el diseño del seguro. La segunda etapa consiste en establecer un índice por sequía hidrológica que tenga un alto grado de correlación con las pérdidas productivas y económicas en las comunidades de regantes y reduzca los problemas de riesgo moral, selección adversa y riesgo base que se presentan en este tipo de seguros indexados. En este caso, se diseñaron y evaluaron tres índices de sequía hidrológica (IEECHJ, ISH1, ISH2), siendo el indicador principal el índice de estado de escasez IEECHJ de la Unidad Territorial UTE del Júcar, establecido en el plan especial de sequía de la Demarcación Hidrográfica del Júcar PES (2018). Finalmente, en la tercera etapa se busca establecer los principales parámetros económicos del seguro: la indemnización recibida, el máximo valor indemnizable y el valor de la prima pura a pagar que se incluirán en los diferentes tipos de contrato.
El seguro es evaluado simulando su operación como si estuviera en funcionamiento. Se utilizan indicadores económicos-financieros para comparar los beneficios para la comunidad de regantes con o sin contrato. Los indicadores utilizados son la desviación estándar, el error cuadrático medio, el índice de siniestralidad y el riesgo base, los cuales están en función del margen bruto del cultivo. Para analizar la gestión del recurso hídrico en la cuenca y determinar escenarios de escasez que pueden declarar un siniestro o pago de indemnización del seguro, se utilizó un modelo de gestión de cuencas que tiene en cuenta las reglas de gestión del sistema.
Al incluir los indicadores financieros en la evaluación del seguro, se determina que la mejor opción en el diseño es tomar el IEECHJ=0.20 sin franquicia deducible como disparador. Esto minimiza la semivarianza y la desviación estándar del margen bruto y permite obtener valores más altos del margen bruto mínimo en comparación con la opción de no implementar el seguro.
El seguro por sequía hidrológica contribuye a llenar el vacío existente en los planes de seguro tradicionales para cultivos bajo riego y ofrece cobertura adicional a los agricultores en condiciones de sequía y escasez de agua. Además, este diseño logra comprender la complejidad de la interacción de los subsistemas de aportaciones, demandas y reglas de operación del recurso hídrico a nivel de cuenca, siendo esta la contribución principal de esta investigación. / [CA] L'escassetat d'aigua és un problema cada vegada més recurrent per a l'agricultura de regadiu a les regions mediterrànies, sent la sequera hidrològica un dels problemes que afecta la disponibilitat d'aigua. Per tant, és necessari establir alternatives tècniques i economicofinanceres que permeten als regants enfrontar aquest problema des d'una visió àmplia de la gestió de l'aigua per a ús agrícola a nivell de conca. Aquestes alternatives han d'incloure instruments de planificació hidrològica, que permeten analitzar l'impacte de la sequera i determinar les mesures a implementar quan el recurs hídric disponible no siga suficient per a satisfer les demandes d'aigua.
Un dels instruments econòmics i financers per a la gestió del risc agroclimàtic que s'ha implementat amb èxit i que cada dia cobra més força és el de les assegurances agrícoles, més específicament, el segur indexat. Així, aquesta investigació pretén contribuir a mitigar l'impacte de l'escassetat d'aigua en comunitats de regants situades en conques altament regulades, com el sistema d'explotació del va riure Xúquer, mitjançant el disseny d'un nou esquema de segur indexat per sequera hidrològica, basat en índexs totalment alineats amb els procediments de gestió de la sequera a nivell de conca.
El procés de disseny del segur comprén 3 etapes. En la primera, s'avalua econòmicament l'impacte de la sequera per a establir una indemnització unitària, element base per al disseny de l'assegurança. Posteriorment, la segona etapa consisteix a establir un índex per sequera hidrològica que tinga un alt grau de correlació amb les pèrdues productives i econòmiques en les comunitats de regants i reduïsca els problemes de risc moral, selecció adversa i risc base que es presenten en aquesta mena d'assegurances indexades. En aquest cas, es van dissenyar i van avaluar tres índexs d'estat d'escassetat (IEECHJ, ISH1, ISH2), sent l'indicador principal l'índex IEECHJ de la Unitat Territorial del Xúquer UTE, establit en el pla especial de sequera de la Demarcació Hidrogràfica del Xúquer PES (2018). Finalment, en la tercera etapa es busca establir els principals paràmetres econòmics de l'assegurança: la indemnització rebuda, el màxim valor indemnitzable i el valor de la prima a pagar que s'inclouran en els diferents tipus de contracte.
El segur és avaluat simulant la seua operació com si estiguera en funcionament. S'utilitzen indicadors econòmics-financers per a comparar els beneficis per a la comunitat de regants amb o sense contracte. Els indicadors utilitzats són la desviació estàndard, l'error quadràtic mitjà, l'índex de sinistralitat i el risc base, els quals estan en funció del marge brut del cultiu. Per a analitzar la gestió del recurs hídric en la conca i determinar escenaris d'escassetat que poden declarar un sinistre o pagament d'indemnització del segur, es va utilitzar un model de gestió de conques que té en compte les regles de gestió del sistema.
En incloure els indicadors financers en l'avaluació del segur, es determina que la millor opció en el disseny és prendre el IEECHJ=0.20 sense franquícia deduïble com disparador. Això minimitza la semivariància i la desviació estàndard del marge brut i permet obtindre valors més alts del marge brut mínim en comparació amb l'opció de no implementar l'assegurança.
L'assegurança per sequera hidrològica contribueix a omplir el buit existent en els plans de segur tradicionals per a cultius sota reg i ofereix cobertura addicional als agricultors en condicions de sequera i escassetat d'aigua. A més, aquest disseny aconsegueix comprendre la complexitat de la interacció dels subsistemes d'aportacions, demandes i regles d'operació del recurs hídric a nivell de conca, sent aquesta la contribució principal d'aquesta investigació. / [EN] Water scarcity is an increasingly recurring problem for irrigated agriculture in the Mediterranean region, with hydrological droughts affecting water availability. Therefore, it is necessary to establish technical and economic-financial alternatives that allow irrigators to face this problem from a broad vision of water management for agricultural use at the basin level. These alternatives should include hydrological planning tools that allow the analysis of the effects of drought and the determination of the measures to be implemented when the available water resources cannot meet the water demand.
One of the economic and financial instruments for managing agro-climatic risks that has been successfully implemented and is gaining more strength every day is agricultural insurance, specifically indexed insurance. This research aims to contribute to the mitigation of the effects of water scarcity in irrigation communities located in highly regulated basins, such as the Júcar river exploitation system, through the design of a new insurance scheme indexed by hydrological drought, based on indices fully aligned with drought management procedures at the basin level.
The insurance design process consists of three stages. First, the impact of drought is economically evaluated to determine a unit compensation, which is the basis for the insurance design. The second stage is to establish a hydrological drought index that is highly correlated with productive and economic losses in irrigation communities and reduces moral hazard problems, adverse selection, and baseline risks problems inherent in this type of indexed insurance. In this case, three indices of scarcity status (IEECHJ, ISH1, ISH2) were designed and evaluated, the main indicator being the IEECHJ index of the Júcar UTE Territorial Unit, established in the Special Drought Plan of the Júcar River Basin PES (2018). Finally, the third stage aims to establish the main economic parameters of the insurance: the compensation received, the maximum compensable value, and the value of the premium rate to be included in the different types of contracts.
The insurance is evaluated by simulating of its operation as if it were in process. Economic-financial indicators are used to compare the benefits to the community of irrigators with and without a contract. The indicators used are standard deviation, mean root-square loss, loss ratio, and base risk, which are based on the gross margin of the crop. The water resources simulation model that considers system management rules was used to analyze water resource management in the basin and to determine scarcity scenarios that could trigger a claim or insurance indemnity payment.
By including financial indicators in the insurance assessment, it is determined that the best option in the design is to consider as a trigger the IEECHJ=0.20 without a deductible franchise, since the semi-variance and standard deviation of the gross margin are minimized, and higher values of the minimum gross margin are obtained compared to the option of not implementing insurance.
Hydrological drought insurance contributes to fill the gap in traditional insurance schemes for irrigated crops and provides additional coverage to farmers in times of drought and water scarcity. In addition, this design manages to understand the complexity of the interaction of the subsystems of contributions, demands and operating rules of the water resource at the basin level, which is the main contribution of this research. / Valenzuela Mahecha, MA. (2023). Diseño de esquema de seguros agrícolas para mitigación del riesgo de sequías hidrológicas mediante modelos hidroeconómicos a escala de cuenca [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/198184
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Performance of Large-Scale Gezira Irrigation Scheme and its Implications for Downstream River Nile FlowAl Zayed, Islam 30 June 2015 (has links) (PDF)
Policy makers adopt irrigated agriculture for food security, since irrigation doubles crop production. Therefore, the development of large irrigation systems has a long history in many places worldwide. Although large-scale irrigation schemes play an important role in improving food security, many schemes, especially in Africa, do not yield the expected outcomes. This is related to poor water management, which is generally due to a lack of effective evaluation and monitoring. The objective of this study, therefore, is to propose a new methodology to assess, evaluate and monitor large-scale irrigation systems.
Information on irrigation indicators is needed to enable the evaluation of irrigation performance. The evaluation is the first and the most significant step in providing information about how it is performing. After reviewing extensive literature, a list of indicators related to the performance of irrigation, rainwater supply and productivity is suggested. The irrigation efficiency indicators Relative Irrigation Supply (RIS) and Relative Water Supply (RWS) are selected. Potential rainwater supply to crops can be tested based on the Moisture Availability Index (MAI) and the Ratio of Moisture Availability (RMA). Water productivity can be assessed by Crop Yield (Y) and Water Use Efficiency (WUE). However, the central problem facing large-scale irrigation schemes is always the lack of data, which calls for the development of a new method of data acquisition that allows evaluation and monitoring. Remote Sensing (RS) technology makes it possible to retrieve data across large areas. Two different approaches via RS, the Normalized Difference Vegetation Index (NDVI) and Actual Evapotranspiration (ETa), can be utilized for monitoring. The well-known Vegetation Condition Index (VCI), derived from the NDVI, is modified (MVCI) to allow a qualitative spatio-temporal assessment of irrigation efficiency. MVCI takes into account crop response to water availability, while ETa indicates whether water is used as intended. Furthermore, the assessment of the possible hydrological impact of the irrigation system should be considered in the evaluation and monitoring process. The Sudanese Gezira Scheme of 8,000 square kilometers in the Nile Basin, where performance evaluation and monitoring are absent or poorly conducted, is no exception. This research takes the large-scale irrigation of the Gezira Scheme as a case study, as it is the largest scheme, not only in the Nile Basin but also in the world, under single management.
The first long-term historical evaluation of the scheme is conducted for the period 1961–2012 rather than only on a short-time scale as is the common practice. An increase in RIS and RWS values from 1.40 and 1.70 to 2.23 and 2.60, respectively, since the 1993/94 season shows decreasing irrigation efficiency. MAI and RMA for summer crops indicate a promising rainfall contribution to irrigation in July and August. The Gezira Scheme achieves low yield and WUE in comparison to many irrigation schemes of the globe. Low productivity is mainly due to poor distribution and irrigation mismanagement. This is indicated by the 15-year MVCI spatio-temporal analysis, which shows that the northern part of the scheme experiences characteristic drought during the summer crop season. Although MVCI can be considered a monitoring tool, the index does not deduct the soil water content, and water could be wasted and available in other ways (e.g. water depressions).
Spatio-temporal information for ETa is required to better quantify water depletion and establish links between land use and water allocation. However, several RS models have been developed for estimating ETa. Thus, improving the understanding of performance of such models in arid climates, as well as large-scale irrigation schemes, is taken into account in this study. Four different models based on the energy balance method, the Surface Energy Balance Algorithm for Land (SEBAL), Mapping EvapoTranspiration at High Resolution with Internalized Calibration (METRIC™), Simplified Surface Energy Balance (SSEB) and MOD16 ET are applied in order to determine the optimal approach for obtaining ETa. Outputs from these models are compared to actual water balance (WB) estimates during the 2004/05 season at field scale. Several statistical measures are evaluated, and a score is given for each model in order to select the best-performing model. Based on ranking criteria, SSEB gives the best performance and is seen as a suitable operational ETa model for the scheme. SSEB subsequently is applied for summer and winter crop seasons for the period 2000–2014.
Unfortunately, one of the limitations faced in the current research is the absence of validation data on a regional scale. Therefore, the assessment focuses on spatial distribution and trends rather than absolute values. As with the MVCI distribution, the seasonal ETa for the Gezira Scheme is higher in the southern and central parts than in the northern part. This confirms the robustness of the developed MVCI. To avoid using absolute values of ETa, the ratio of ETa from agricultural areas (ETagr) to the total evapotranspiration (ET) from the scheme (ETsum) is calculated. The ETagr/ETsum ratio shows a descending trend over recent years, indicating that the water is available but not being utilized for agricultural production.
This study shows that SSEB is also useful for identifying the location of water losses on a daily basis. Around 80 channels are identified as having leakage problems for the 2013/14 crop season. Such information is very useful for reducing losses at the scheme. In addition, Rainwater Harvesting (WH) is addressed and found to be applicable as an alternative solution for accounting for rainfall in irrigation. It is seen that these management scenarios could save water and increase the overall efficiency of the scheme. It is possible to save 68 million cubic meters of water per year when the overall irrigation efficiency of the scheme is improved by only 1%. A level of efficiency of 75% is predicted from the proposed management scenarios, which could save about 2.6 billion cubic meters of water per year.
In conclusion, the present study has developed an innovative method of identifying the problems of large-scale schemes as well as proposing management scenarios to enhance irrigation water management practice. Improved agricultural water management in terms of crop, water and land management can increase food production, thereby alleviating poverty and hunger in an environmentally sustainable manner.
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Performance of Large-Scale Gezira Irrigation Scheme and its Implications for Downstream River Nile FlowAl Zayed, Islam 22 June 2015 (has links)
Policy makers adopt irrigated agriculture for food security, since irrigation doubles crop production. Therefore, the development of large irrigation systems has a long history in many places worldwide. Although large-scale irrigation schemes play an important role in improving food security, many schemes, especially in Africa, do not yield the expected outcomes. This is related to poor water management, which is generally due to a lack of effective evaluation and monitoring. The objective of this study, therefore, is to propose a new methodology to assess, evaluate and monitor large-scale irrigation systems.
Information on irrigation indicators is needed to enable the evaluation of irrigation performance. The evaluation is the first and the most significant step in providing information about how it is performing. After reviewing extensive literature, a list of indicators related to the performance of irrigation, rainwater supply and productivity is suggested. The irrigation efficiency indicators Relative Irrigation Supply (RIS) and Relative Water Supply (RWS) are selected. Potential rainwater supply to crops can be tested based on the Moisture Availability Index (MAI) and the Ratio of Moisture Availability (RMA). Water productivity can be assessed by Crop Yield (Y) and Water Use Efficiency (WUE). However, the central problem facing large-scale irrigation schemes is always the lack of data, which calls for the development of a new method of data acquisition that allows evaluation and monitoring. Remote Sensing (RS) technology makes it possible to retrieve data across large areas. Two different approaches via RS, the Normalized Difference Vegetation Index (NDVI) and Actual Evapotranspiration (ETa), can be utilized for monitoring. The well-known Vegetation Condition Index (VCI), derived from the NDVI, is modified (MVCI) to allow a qualitative spatio-temporal assessment of irrigation efficiency. MVCI takes into account crop response to water availability, while ETa indicates whether water is used as intended. Furthermore, the assessment of the possible hydrological impact of the irrigation system should be considered in the evaluation and monitoring process. The Sudanese Gezira Scheme of 8,000 square kilometers in the Nile Basin, where performance evaluation and monitoring are absent or poorly conducted, is no exception. This research takes the large-scale irrigation of the Gezira Scheme as a case study, as it is the largest scheme, not only in the Nile Basin but also in the world, under single management.
The first long-term historical evaluation of the scheme is conducted for the period 1961–2012 rather than only on a short-time scale as is the common practice. An increase in RIS and RWS values from 1.40 and 1.70 to 2.23 and 2.60, respectively, since the 1993/94 season shows decreasing irrigation efficiency. MAI and RMA for summer crops indicate a promising rainfall contribution to irrigation in July and August. The Gezira Scheme achieves low yield and WUE in comparison to many irrigation schemes of the globe. Low productivity is mainly due to poor distribution and irrigation mismanagement. This is indicated by the 15-year MVCI spatio-temporal analysis, which shows that the northern part of the scheme experiences characteristic drought during the summer crop season. Although MVCI can be considered a monitoring tool, the index does not deduct the soil water content, and water could be wasted and available in other ways (e.g. water depressions).
Spatio-temporal information for ETa is required to better quantify water depletion and establish links between land use and water allocation. However, several RS models have been developed for estimating ETa. Thus, improving the understanding of performance of such models in arid climates, as well as large-scale irrigation schemes, is taken into account in this study. Four different models based on the energy balance method, the Surface Energy Balance Algorithm for Land (SEBAL), Mapping EvapoTranspiration at High Resolution with Internalized Calibration (METRIC™), Simplified Surface Energy Balance (SSEB) and MOD16 ET are applied in order to determine the optimal approach for obtaining ETa. Outputs from these models are compared to actual water balance (WB) estimates during the 2004/05 season at field scale. Several statistical measures are evaluated, and a score is given for each model in order to select the best-performing model. Based on ranking criteria, SSEB gives the best performance and is seen as a suitable operational ETa model for the scheme. SSEB subsequently is applied for summer and winter crop seasons for the period 2000–2014.
Unfortunately, one of the limitations faced in the current research is the absence of validation data on a regional scale. Therefore, the assessment focuses on spatial distribution and trends rather than absolute values. As with the MVCI distribution, the seasonal ETa for the Gezira Scheme is higher in the southern and central parts than in the northern part. This confirms the robustness of the developed MVCI. To avoid using absolute values of ETa, the ratio of ETa from agricultural areas (ETagr) to the total evapotranspiration (ET) from the scheme (ETsum) is calculated. The ETagr/ETsum ratio shows a descending trend over recent years, indicating that the water is available but not being utilized for agricultural production.
This study shows that SSEB is also useful for identifying the location of water losses on a daily basis. Around 80 channels are identified as having leakage problems for the 2013/14 crop season. Such information is very useful for reducing losses at the scheme. In addition, Rainwater Harvesting (WH) is addressed and found to be applicable as an alternative solution for accounting for rainfall in irrigation. It is seen that these management scenarios could save water and increase the overall efficiency of the scheme. It is possible to save 68 million cubic meters of water per year when the overall irrigation efficiency of the scheme is improved by only 1%. A level of efficiency of 75% is predicted from the proposed management scenarios, which could save about 2.6 billion cubic meters of water per year.
In conclusion, the present study has developed an innovative method of identifying the problems of large-scale schemes as well as proposing management scenarios to enhance irrigation water management practice. Improved agricultural water management in terms of crop, water and land management can increase food production, thereby alleviating poverty and hunger in an environmentally sustainable manner.
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