A GIS-based user-interface programme was developed to compute the geospatial Water ProductivityIndex (WPI) of a river-fed rice irrigation scheme in Northwest Selangor, Malaysia. The spatial analysisincludes irrigation blocks with sizes ranging from 20 to 300 ha. The amount of daily water use for eachirrigation block was determined using irrigation delivery model and stored in the database for both mainseason (August to December) and off season (February to May). After cut-off of the irrigation supply,a sub-module was used to compute the total water use including rainfall for each irrigation block. Therice yield data for both seasons were obtained from DOA (Department of Agriculture, Malaysia) of thescheme. Then, the Water Productivity Index (WPI) was computed for each irrigation block and spatialthematic map was also generated. ArcObjects and Visual Basic Application (VBA) programminglanguages were used to structure user-interface in the ArcGIS software. The WPI, expressed in termsof crop yield per unit amount of water used (irrigation and effective rainfall), ranged from 0.02 to 0.57kg/m3 in the main season and 0.02 to 0.40 in off season among irrigation blocks, respectively. Thedevelopment of the overall system and the procedure are illustrated using the data obtained from thestudy area. The approach could be used to depict the gaps between the existing and appropriate watermanagement practices. Suitable interventions could be made to fill the gaps and enhance water useefficiency at the field level and also help in saving irrigation water through remedial measures in theseason. The approach could be useful for irrigation managers to rectify and enhance decision-makingin both the management and operation of the next irrigation season.
One of the most interesting water management case studies in Iran is the case of Zayandehrud River, the main river that supplies water to Isfahan Province which is located in Gavkhuni River Basin (GRB). This paper examines the present and future demands for water and determines the extent to which water will be available for agricultural use by the year 2020. Although demand and supply conditions in 2000 were more or less in balance, there was an increase in the supply of some 28% by 2010 due to the completion of the third trans-basin diversion and the development of other local water sources. However, the demand exceeded its supply in 2010 and the basin fell into severe deficit. In this condition, the only way to keep supply and demand in balance is to reduce allocations to agriculture. By 2020, agriculture would only have 5% more water than the present and water supply is only 90% that of the normal, and this would then shrink from 2025 onwards. In other words, agriculture would have to be sacrificed in order to ensure full supplies of water for the other sectors. The scenarios examined reveal that a sustainable agriculture can only be accomplished by water saving practices and management measures, which may further lead to reduced demand, control supplies, and improve the efficiency of water use.
The hydrological effects of climate variation and land use conversion can occur at various spatial scales, but the most important sources of these changes are at the regional or watershed scale. In addition, the managerial and technical measures are primarily implemented at local and watershed scales in order to mitigate adverse impacts of human activities on the renewable resources of the watershed. Therefore, quantitative estimation of the possible hydrological consequences of potential land use and climate changes on hydrological regime at watershed scale is of tremendous importance. This paper focuses on the impacts of climate change as well as land use change on the hydrological processes of river basin based on pertinent published literature which were precisely scrutinized. The various causes, forms, and consequences of such impacts were discussed to synthesize the key findings of literature in reputable sources and to identify gaps in the knowledge where further research is required. Results indicate that the watershed-scale studies were found as a gap in tropical regions. Also, these studies are important to facilitate the application of results to real environment. Watershed scale studies are essential to measure the extent of influences made to the hydrological conditions and understanding of causes and effects of climate variation and land use conversion on hydrological cycle and water resources.
Competition for limited available water for crop production is an ever-increasing issue for
farmers due to increasing demand of irrigation water worldwide. Due to high energy cost
in operating pressurized irrigation systems, energy-efficient low-pressure wick irrigation
systems can play important roles for smallholder greenhouse crop production by ensuring
higher water use efficiency than most traditional approaches. The objectives of this study
were to investigate HYDRUS 2D-simulated water distribution patterns in soil and soilless
growing media, and to evaluate water balance in these media under capillary wick irrigation
system. To accomplish these objectives, eggplants (Solanum melongena L.) were grown
in potted peatgro and sandy clay loam in a greenhouse experiment, water distribution was
simulated by using HYDRUS 2D software package and compared with the measured
values, and water uptake by the plant roots was determined for water balance calculation.
The wetting pattern was found axially symmetric in both growing media (peatgro and
soil) under the wick emitters. The simulated
water distribution in both growing media
revealed dependency of spatial extent of the
wetted zone on water application period and
hydraulic properties of the media. The mean
absolute error (MAE) in water content over
depth varied from 0.04 to 0.10 m3 m−3 and the root mean square error (RMSE) varied from 0.04 to 0.11 m3 m−3. Deviations between the
measured and simulated water contents in the peatgro medium were larger over depth than
over lateral distance. In contrast, the model criteria matched well for the sandy clay loam
and provided MAE of 0.01 to 0.02 m3 m−3 and RMSE of 0.01 to 0.03 m3 m−3, indicating
good agreement between the measured and simulated water contents.