The Ganges Delta in Bangladesh, a transboundary rural river basin, is an example of water-related calamities due to natural and human-induced stresses. It is an agriculture-dominated area with the presence of Sundarbans mangrove forest. Recently this area is facing unfavorable conditions due to limitations in quantity, quality, and timing of available freshwater. As a result, floods, droughts, water scarcity, stream depletion, salinity intrusion, excessive sedimentation are becoming common phenomena. These calamities are making this area unsuitable for agriculture and vulnerable to the Sundarbans’ ecosystem. This study aims to provide technical insight into issues related to water scarcity and projected agricultural water demand for 2020-2100 considering the climate change uncertainties. We addressed three critical areas to attain this purpose. As a first task, this study attempted to analyze and understand the observed hydrological changes over the past six decades to fathom the critical reasons for freshwater scarcity. Secondly, interdependency, availability, and accessibility of surface water and groundwater were analyzed to investigate the adequacy of current water demand and supply in agriculture, industrial and domestic sectors. Irrigation demand is much higher than others and occupies 93% of the total water demand. Similarly, irrigation is 96% of total water withdrawal. This high demand in the agriculture sector led to our next objective to estimate agricultural demand for this century. It helps to understand an overall agricultural water consumption scenario for the future. This study provides necessary background information, which is vital for hydro-economically feasible agricultural water management plans.

Limited freshwater supply is the most important challenge in water resources management, particularly in arid and semi-arid basins. However, other variations in a basin, including climate change, population growth, and economic development intensify this threat to water security. The Oldman River Basin (OMRB), located in southern Alberta, Canada, is a semi-arid basin and encompasses several water challenges, including uncertain water supply as well as increasing, uncertain water demands (consumptive irrigation, municipal, and industrial demands, and non-consumptive hydropower generation, and environmental demands). Reservoirs, of which the Oldman River Reservoir is the largest in the basin, are responsible for meeting most of demands, and, protecting the basin’s economy. The OMRB has also faced extreme natural events, floods and droughts, in the past, which reservoir management plays a critical role to adapt to. The complexity of the climate, hydrology, and water resource system and water governance escalates the challenges in the basin. These factors are highly interconnected and establish dynamic, non-linear behavior, which requires an integrated, feedback-based tool to investigate. Integrated water resources (IWRM) modelling using system dynamics (SD) is such an approach to tackle the different water challenges and understand their non-linear, dynamic pattern. In this research study the Sustainability-oriented Water Allocation, Management, and Planning (SWAMPOM) model for the Oldman River Basin is developed. SWAMPOM comprises a water allocation model, dynamic irrigation demand, instream flow needs (IFN), and economic evaluation sub-models. The water allocation model allocates water to all the above-mentioned demands at a weekly time step from 1928 to 2001, and under different water availability scenarios. Meeting irrigation demands relies on the crop water requirement (CWR), which is calculated under different climatic conditions by the dynamic irrigation demand sub-model. This sub-model estimates the weekly irrigation demand for main crops planted in the basin. SWAMPOM also computes environmental demands or instream flow need (IFN) for the Oldman River, and allocates water to rivers to meet IFN under different policy scenarios and uncertain water supply. Finally, the major water-related economic benefit in the basin, earned by agriculture and hydropower generation, is computed by the economic evaluation sub-model. The results show that SWAMPOM could reasonably satisfy the demands at a weekly time step and provide an adequate estimation of the crop water requirement under different hydrometeorological conditions. Based on the SWAMPOM’s results, the average annual irrigation demand is 306 mm over the historical time period from 1928 to 2001 in the main irrigation districts. The average weekly instream flow need of the Oldman River is calculated to be approximately 20.5 m3/s, which can be met in more than 97% of weeks in the historical time period. Average annual water-related economic benefit was computed to be 192.5 M$ in the OMRB. It decreased to 82.8 M$ in very dry years, and increased up to 328.6 M$ in very wet years. This research also developed different sets of Oldman Reservoir’s operation zones, resulting in trade-offs between the optimal economic benefit, water allocated to the ecosystem, minimum floodwater and minimum flood frequency. This helps decision makers to decide how much water should be stored in the reservoir to meet a specific objective while not sacrificing others. A multi-objective performance assessment, Pareto curve approach, is applied to identify the optimal trade-offs between the four objective functions (OFs), and 18 different optimal, or close to optimal sets of operating zones are provided. The decision regarding the operating zones depends on decision makers’ preference for higher economic benefit, water allocated to IFN, or flood security. However, the set of operating zones with minimum floodwater causes 11 less flood events; the operating zones with maximum economic benefits result in 4.1% more financial gain; and the zones with maximum water allocated to IFN lead to 10.1% more ecosystem protection in the whole 74 years, compared to current zones.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-06-04T18:21:18Z No. of bitstreams: 1 SOAHD ARRUDA RACHED FARIAS - TESE PPGEA 2006..pdf: 106641017 bytes, checksum: 00962c5527d6dea906019cefb658d12c (MD5) / Made available in DSpace on 2018-06-04T18:21:18Z (GMT). No. of bitstreams: 1 SOAHD ARRUDA RACHED FARIAS - TESE PPGEA 2006..pdf: 106641017 bytes, checksum: 00962c5527d6dea906019cefb658d12c (MD5) Previous issue date: 2006-10 / Propõe-se, no presente trabalho, uma avaliação de custos de energia e água. dentro do planejamento agrícola irrigado obtendo-se, inicialmente, as demandas brutas de água e energia para as culturas do coco anão (Cocos nucifera L.), mamão {Carica papayá) e banana pacovã {Musa spp) em 14 municípios do Nordeste Brasileiro e se utilizando dois sistemas pressuridados, através de uma simulação de projeto agronómico de irrigação. O menor consumo de água anual previsto para irrigação foi na localidade de Mamanguape, PB, necessitando-se apenas de 37,4%; 35,5% e 41,4% respectivamente, para as culturas de coco anão, mamão e Banana pacovã, com relação ao consumo obtido na localidade de maior consumo (Petrolina, PE). Obtiveram-se áreas potenciais para irrigação empregando-se o mesmo conjunto eletrobomba (7,5 CV e vazão de 22 m3 h"1) para as culturas de coco anão, mamão e banana pacovã, respectivamente, de 13,65 ha (localizada) e 4,54 ha (aspersão); 9,45 ha (localizada) e 5,18 ha (aspersão) e 6,25 ha (localizada) e 3,63 ha (Aspersão). A crescente demanda de água e energia ocorreu praticamente combinada pela escala de classificação climática de Hargreaves (1974b), onde percorreu a menor necessidade de complementação o município dc Mamanguape, PB (Clima Seco-Úmido), sequenciado, Pacatuba, SE, Maceió, AL, Aracaju, SE, Natal, RN, Campina Grande, PB, posteriormente os municípios Acaraú, CE, Aracati, CE e Touros, RN de clima Semi-Arido, Canindé de São Francisco, SE, Sousa, PB e Jaguaribe, CE com clima Árido e Açu, RN e Petrolina, PE classificados como de clima Muito Árido. A cultura do coco anão seria a mais penalizada economicamente pela cobrança da água, em virtude do menor custo de manutenção com relação às outras duas culturas da análise. Os valores obtidos através deste estudo poderão ser utilizados como parâmetros de planejamento agrícola irrigado, com maior confiabilidade, quando as médias obtidas, forem agrupadas por clima e os coeficientes de variação apresentarem valores baixos (menor que 10%), desde que tenham características de dimensionamento semelhantes às deste trabalho. E importante observar o comportamento de demanda de irrigação como forma de se avaliar atribuições de tarifa de água bruta, evitando possíveis distorções económicas decorrentes de climas diferenciados em uma mesma bacia hidrográfica / It is considcred, in the present work, an evaluation of costs of energy and water. inside o; the agricultural irrigated planning, getting at first the raw demands from water and energy for the cultures of the dwarfed coconut (Cocos nucifera L.), papaya (Carica papaya) and pacovã banana (Musa spp) in 14 cities from northeast Brazil and if used two pressured systems, through a simulation of agronomic project of irrigation. The lesser foresecn annual water consumption for irrigation was in the locality of Mamanguape, PB, needing itself only 37.4%; 35.5% and 41.4% respectively, for the cultures of dwarfed coconut, papaya and pacovã Banana, based on the consumption gotten in the locality of bigger consumption (Petrolina, PE). Areas with good chance for irrigation had gotten the same using electropumps (7.5 CV and 22 outflow of m3 h"1) for the cultures of dwarfed coconut, papaya and pacovã banana, respectively, of 13.65 ha (located) and 4.54 ha (aspersion); 9,45 ha (located) and 5,18 ha (aspersion) and 6.25 ha (located) and 3.63 ha (Aspersion). The increasing demand of water and energy practically occurred combined by the scale of climatic classification of Hargreaves (1974b), whcre the city of Mamanguape PB (Dry-Wet climate), covered the lesser needs for complementation, following with Pacatuba, SE, Maceió, AE, Aracaju, SE, Natal, RN, Campina Grande, PB, later the cities Acaraú, CE, Aracati, CE and Touros, RN of Semi-Arid climate, Canindé do São Francisco, SE, Sousa, PB and Jaguaribe, CE, with Arid climate and Açu, RN and Petrolina, PE classified as of Very Arid climate. The culture of the dwarfed coconut would be punished economically by the water taxes, because of the lesser cost of maintenance related to the others two cultures in analysis. The values gotten through this study could be used as parameters for irrigated agricultural planning, with bigger trustworthiness, when the gotten averagcs, will be grouped by climate and the coefficients of variation will present low values (lesser than 10%), since they have similar sizing characteristics to the ones of this work. It is important to observe the behavior of irrigation demand as a way of evaluating attributions of raw water taxes, avoiding possible economic distortions due to differentiated climates in one same hidrografic basin.