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The Skudai River has experienced a general decline in water quality over the last several years due to agricultural practices, economic development, and other human activities in the river catchment. The spatial trend of water quality index (WQI) and its sub-indexes are important for determining the locations of major pollutant sources that contribute to water quality depletion in the Skudai and its tributaries. In this study, we have developed WQI for eight sections of the Skudai watershed. Ammonia-nitrogen (NH 3 -N) was identified as a major pollutant downstream from the Skudai, with the lowest WQI index (i.e. 38). WQI for the Skudai (natural) was 94, i.e., Class I (very clean) category of river water quality. The Senai River has WQI value of 85 and Class II category (slightly polluted). However, the Kempas River, which was in suburban parts of the Skudai watershed, had WQI of 53 (Class III, polluted). The Melana and Danga rivers were also polluted rivers with WQI of 69 and 57, respectively, in Class III (polluted). Overall water quality in the Skudai and its tributaries was downstream of the river. The study also assessed water quality of the Skudai and its tributaries from other water quality parameters such as conductivity, turbidity, temperature, total dissolved solids, total phosphorous, and nitrogen, which were not part of the WQI formula developed by the Department of the Environment (DOE), Malaysia. The study found that Department of Education (DOE) formula for WQI was not effective in water quality assessment as many important parameters such as nutrients, heavy metals, and fecal coliform (or E. Coli) were missing in the WQI formula.

A field experiment was carried out to evaluate the effect of irrigation regimes and nitrogen levels on the growth and yield of wheat cv. Kanchan (Triticum aestivumL.). The experiment includes two factors such as four irrigation regimes and four nitrogen levels. Three farmer’s fields were selected for experimentation as replication. Yield and yield contributing factors were significantly affected by irrigation regimes and different doses of nitrogen. Maximum grain yield of 2.27 t ha−1by the application of 200 mm irrigation treatment. Interaction between 200 mm irrigation and 120 kg N ha−1was the best combination treatment.

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The rotational irrigation water delivery (warabandi) system practiced in the Indus river basin of Pakistan has continued for 100 years. Irrigation water allocated to the farmers under the warabandi system is proportional to farm size and is fixed. This rigid allocation system has been partly justified by its contribution to social equity though this may have been at the cost of economic gains. In order to assess the operation of warabandi's basic rules, a farmers' survey was completed from 124 farmers located on five watercourses. A questionnaire was administered to each farmer and farm management data were gathered. As fresh water resources are under stress and becoming scarce their efficient use in all applications should be assured in water allocations. It is shown from the survey results that water allocation based on very limited criteria does not maximize the socio-economic benefits gained from the use of scarce water. Thus, it is suggested that the existence or nonexistence of fresh groundwater resources along with other critical variables should be taken into consideration when making canal water allocation decisions. Missed water deliveries due to failure of the canal system appear to be the largest cause of losses. Water charges need to be increased to fund large improvements in canal maintenance programs. It is pointed out that a framework should be developed as a tool to improve water productivity for Pakistan. This should include: consideration of the gross area of a tertiary canal, sensitivity of crop growth stage to water shortage, crop value, bias of allocation towards most water use efficient areas and water use efficient crops, the potential losses from water deficiency.