Water is the driving force of all nature”, as a result of which it has become a new source of conflict between domestic, industrial and agricultural users of water. Indeed, man has been using all his ingenuity not only to explore water resources but also to manage it efficiently. It is reported that global water withdrawals accelerated sharply during the 20th century and that they even increased in excess of the population growth. Thus, in the recent past, water resource management has become fundamental to human existence and economic development.

One of the commonest techniques of managing water resources is raising barriers across the natural flow of river water system and diverting it for irrigating agricultural fields so as to maximize the productivity of land. A weir is a low head dam commonly used to raise the level of a river. The crest of an overflow spillway on a large dam is also called a weir. These are mainly designed to create mill ponds and water flows over the top of a weir. The capacity of a weir refers to the discharge for a given head of flow over its crest. To augment the capacity of a weir, labyrinth weir is created, for it has certain advantages—helps in managing water level control in flat lines. Labyrinths are the weirs in which crest length is made significantly longer than the width of the river by having a plan form consisting of repeating geometric cycles, typically trapezoidal in form. If it is used in a canal system, it serves as an energy dissipator, besides maintaining a more constant flow depth in the canal, in comparison to a conventional structure.

The author, S M Yadav, of the first paper of the issue, “Coefficient of Discharge for Double and Triple Cycle Labyrinth Weir”, has proposed a mathematical model to design a double and triple cycle labyrinth weir based on experimental results. The author had constructed a concrete flume and installed a double and triple cycle labyrinth weir at 25° labyrinth angle—following Tullis’s guidelines. The whole setup was erected as a re-circulatory model. The desired flow was controlled using valves. Head was measured above the weir. The results obtained from the experiments were analyzed using Origin 7.5 software. Finally, a mathematical model was proposed using the experimental data, both for double cycle and triple cycle labyrinth. The author concluded that the coefficient of discharge decreases with the increase in H/P ratio and the value of coefficient of discharge is more for same H/P ratio for double cycle labyrinth weir, compared to triple cycle labyrinth weir.

Owing to many developmental activities, many changes are occurring in soil erosion in the upstream river basins, its transport and deposition, which have an impact on the river system, reservoirs, estuaries and coastal regions. In this context, the authors, Chandramohan T and Balchand A N, of the second paper, “Sediment Yield Characteristics of a Tropical River Basin”, have studied the sediment yield characteristics and its spatial and temporal variation in the Pamba river basin—a major river of the State of Kerala. The daily discharge sediment data of the Central Water Commission was used for the analysis. The study revealed that the water and sediment transported by the river was showing a decreasing trend. The average sediment yield was estimated to be 79 tons/km2, which is comparatively lower vis-à-vis other major river systems in India. The authors have also presented the hysteresis effect of discharge sediment concentration relationship, with a comment that a majority of rainfall events produced clockwise loop.

The authors, Deepak T J, M s m Amin, Rashid Shariff and Rahman Ramli of the third paper, “Webpipa: A Decision Support System for Rice Irrigation Water Management”, have explored the possibility of using WebPIPA as a platform for allowing public participation in disputes regarding water allocation for rice cultivation and resolving the conflicts arising out of water allocation efficiently with active public participation. The authors successfully developed a WebPIPA model for the tertiary canal-based water user groups with the plot numbers alongside to allocate water without wastage. The Internet-based irrigation water resource management model developed by the authors is claimed to be well suited for improving the agriculture productivity of the nation.

The authors, Charles Bong Hin Joo and Ayob Katimon, of the fourth paper, “Non-Darcian Transmission of Water Properties in Malaysian Peat Soil”, have attempted to assess the validity of Darcy’s law for flow through peat soil column in comparison with the macroscopic velocities predicted by Darcy’s law and the observed macroscopic velocities. They have also assessed the suitability of Izbash’s law to predict the flow through peat soil column of different degrees of decomposition. Their results show that Darcy’s law is appropriate only for the upper layer, while Izbash’s law provides a much better approximation of water flow through much deeper peat layers.

The authors, M S Hadda, M Vashistha and Dapinder Pal Singh of the next paper, “Soil Characteristics and Maize Yield as Affected by Soil Management Practices in the Foothills of Shivaliks”, have carried out an experiment to study the effect of soil management practices on some soil characteristics and yield of maize crop in the foothills of Shivaliks. The experimental results indicate that soil management practices such as contour bunding and cultivation across the slope, cultivation of leveled land have significantly improved the status of organic C, total N, available P, CEC, Ca and Mg content respectively, which in turn has improved the maize yield over the control.

The authors, M J Singh, S K Dhillon and K S Dhillon, of the last paper, “Selenium Concentration in Fodder Crops as Affected by the Application of Gypsum and Phosphate Fertilizer”, have assessed the effect of gypsum and phosphate fertilizers on selenium concentration in berseem and sorghum crops in the seleniferous region of Punjab and found gypsum application to be an economically viable option for reducing selenium accumulation by forage crops.

-- GRK Murty
Consulting Editor