Due to the climate change the efficient use of fresh water has become a hot issue. One of the ways to collect water that could otherwise be wasted, is the water harvesting technique. These techniques have been known for centuries and widely applied in the Middle East. This paper presents a simple and easy-to-use water-balance based rainwater harvesting model called WHCatch. It has been designed to investigate the effects of water harvesting on the catchment scale. The catchment is divided into several sub-catchments which can store water for the purpose of water harvesting. The model has been created as a simple Excel workbook with some VBA-code for the computations. Results are presented in the same workbook as separate worksheets. Graphical presentations are created automatically. The capabilities of the workbook are presented and examples of in-and output are shown. Due to its flexibility, the model is suitable to show the effects of climate change as well. It is especially suitable to visualize the effects of measures.

Oscillating reactions are one of the most interesting topics in chemistry and analytical chemistry. Fluctuations in concentrations of one the reacting species (usually a reaction intermediate) create an oscillating chemical reaction. In oscillating systems, the reaction is far from thermodynamic equilibrium. In these systems, at least one autocatalytic step is required. Developing an instinctive feeling for how oscillating reactions work will be invaluable to future generations of chemists. Some software programs have been released for simulating oscillating systems; however, the algorithm details of such software are not transparent to chemists. In contrast, function of spreadsheet tools, like Microsoft Excel, is well understood, and the software is nearly universally available. In this work, the simulation and visualization of different oscillating systems are performed using Microsoft Excel. The simple repetitive solving of the ordinary differential equation of an autocatalytic reaction (a spreadsheet row) followed by time, easily automated by a subroutine (a “ Macro” in Excel), readily simulates an oscillating reaction. This permits the simulation of some oscillating systems such as Belousov-Zhabotinsky. The versatility of an easily understandable computational platform further enables the simulation of the effects of linear and nonlinear parameters such as concentrations of reactants and catalyst, and kinetic constants. These parameters are readily changed to examine their effects.

The length of the steady Gradually Varied Flow (G.V.F) profile in a circular gravity pipe section is computed using the Graphical Integration Method. The equations used for the solution are: a) the dynamic equation of Gradually Varied Flow in a prismatic channels, b) the hydraulic exponents M and N equation derived by Chow [2], and c) the Varied hydraulic exponents M (y/do) and N(y/do) equation modified by Zaghloul [15]. The results of the calculated G.V.F profile length using the modified hydraulic exponents M(y/do) and N(y/do) equation are closer to the G.V.F length calculated based on the exact formulation of the G.V.F dynamic equation. The percentage difference ranges from 0.67% to 8.72% for various bed slopes and G.V.F depth limits. The calculated G.V.F profile length using the Chow hydraulic exponents M and N resulted in wider values with percentage difference ranges from 0.16 to 25.59%. Hence, a remarkable improvement of the computation of G.V.F profile is achieved using the modified M(y/do) and N(y/do) hydraulic exponents.The unsteady Gradually Varied Flow wave propagation in circular gravity pipe section is simulated using the Explicit Method. The Extended Transport block (EXTRAN) of the latest Storm Water Management Model (PCSWMM2000) was used to route the wave through a circular gravity pipe section. The resulting routed hydrographs by the Explicit Method and the EXTRAN Block of the PCSWMM 2000, provided similar flow peak and lag time in both cases.A computer package was developed for the Steady G.V.F length calculation for gravity pipes using the Microsoft Excel spreadsheet. The results are plotted using the Excel graphics capabilities.A second computer package using Microsoft Excel was developed for the Unsteady G.V.F simulation based on the Explicit Method. The routed hydrographs arc plotted by the Excel graphics capabilities.The Excel packages for the Steady and Unsteady G.V.F are user friendly and are posted on the Internet Website location http://briefcase.yahoo.com/civil engineering2001.ARead me File is provided for each Excel package and is used as a users guide.

Small-scale dairy farming in Bangladesh is constrained mostly due to acute shortage, high price and seasonal fluctuation of energy and protein supplements. Poor economic conditions of dairy farmers do not allow them to purchase adequate conventional energy and protein supplements. Locally available non-conventional energy and protein sources can be used as alternatives, cheaper than conventional energy and protein sources. Non-conventional feedstuffs are deficient in certain macro and micro nutrients. As a result, formulation of a least-cost balanced ration using non-conventional feedstuffs is a major challenge for marginal farmers. The current study presents a least-cost formulation plan for the small-scale dairy farmers using locally available low-cost non-conventional feedstuffs. A simple Microsoft Excel program with ‘Solver Add-ins’ has been used to formulate least-cost rations for crossbred and indigenous dairy cows. The step by step logical procedure ensured that the ration was balanced for most of the key nutrients, was least-cost and gave the user significant control over the formulation process. Incorporation of multipurpose low cost neglected forages such as water hyacinth (Eichhornia crassipes), helencha (Enhydra fluctuans), ipil-ipil (Leucaena leucocephala) and their subsequent effect on cost minimization is discussed. This formulation method may be recommended for use by small-scale dairy farmers as well as livestock extension workers who wish to formulate least-cost dairy rations using locally available feed sources to optimize the feeding of dairy animals at farm level.