Constant Discharge Method Research Articles

Assessment of drip lateral design methods based on uniformity coefficient

In this paper, six drip lateral design methods were selected and a comparative assessment was done to find its practical applicability for finding accurate uniformity coefficient. Step-By-Step (SBS) method, Differential method (DM), Constant Discharge method (CDM), Variable discharge method (VDM), Outlet variation method (OVM) and Statistical method (STM) were the different methods assessed. The percentage relative error in calculating the uniformity coefficient by different methods were obtained as the difference between step-by-step method (true) value and alternate method (observed) value. These errors were tabulated. VDM and OVM method performed well with equal accuracy to SBS method at different slopes. For L=250m, DM method performed well. The STM performed good for down slope and lateral length of 250m with 6 per cent relative error. The method having lesser relative percentage error can be selected by the design engineers for designing the laterals from the relative percentage error tables.

Electrical analogue for discharge versus time analysis in a pumping well

Novel findings about the general properties of an aquifer were obtained by applying the pumping approach introduced by Summa (2010). The approach of keeping the pump’s rotation speed constant was chosen over the well-known and widely used constant discharge method. The present analysis was performed on a set of unpublished data acquired during the same field test that was described in Summa (2010). The values of the instantaneous discharge and instantaneous drawdown were obtained. The contribution of the water already stored in the well to the overall capacitance of the aquifer was cancelled out for the field data that were processed. It was then possible to obtain a discharge-time function depending only upon the aquifer discharge. The discharge-time curve that was obtained showed a behaviour practically indistinguishable from the discharge-time curve for a resistor-inductor-capacitor (RLC) circuit with a direct current. By fully exploiting that circuit analogy, it was possible to evaluate the resistance, capacitance and inductance (inertia) of the aquifer. These parameters were estimated from the RLC solution that best fit the discharge-time curve. The value of the hydraulic resistance that was obtained was of the same order of magnitude as the inverse value of the transmissivity, already calculated for the same aquifer in previous work. This matching suggests that this model, as a future development of the present study, can be tested against the standard models regarding the determination of the traditional hydrogeological parameters. Summa G (2010) A new approach to the step-drawdown test, Water SA, 36(3):279–286.

CHARACTERIZATION OF SOIL PERMEABILITY IN PRAMBANAN TEMPLE YARD BASED ON DEVELOPMENT OF IN SITU TEST

Prambanan Temple is a cultural site which has been declared as world cultural heritage that is required to be conserved. Due to heavy equipment activities during maintenance period after Yogyakarta earthquake in May, 2006, soil in temple yard become dense, and ponding occurred after rainfall. A poodle layer and a drainage system has ever built to avoid such a problem, but the pond still didn’t stop appearing after rain. Permeability parameter needs to be characterized to find exact method of solution. This experiment used Constant Discharge method which suitable for permeability test of sandy soil. The procedure were carried out from unsaturated until saturated soil condition. Volumetric water content were being monitored by using soil moisture probe. The results were value of permeability coefficient from unsaturated until saturated condition. The value of permeability coefficient and soil type characterization was mapping based on geographic reference using software Arcview GIS 3.3. Developed instruments were quite efficient and easy to be implemented on determining field soil permeability coefficient of sandy soil. Using constant discharge model, the value of unsaturated soil permeability can be obtained without establishing the matrix suction. The result of soil permeability characterization mapping can be used to determine the alternative solution of the ponding problem.

Nutrient runoff from a Korean rice paddy watershed during multiple storm events in the growing season

Summary The concentrations and loading characteristics of total nitrogen (TN) and total phosphorous (TP) in runoff from a 50.1-ha rice paddy field watershed in South Korea were investigated for eight storm events during the 1998–2001 growing seasons. TN concentrations in total runoff were inversely related to discharge, except in periods with high fertilization rates. In contrast, TP concentrations were strongly proportional to discharge under non-ponded paddy conditions, but not correlated with discharge under most ponded paddy conditions. Stormflow and irrigation return flow were separated from total runoff using the constant-discharge method. The flow-weighted mean TN concentration in stormflow was lower than that in irrigation return flow, mainly because of rainwater dilution, except for periods with a residual fertilizer effect. The flow-weighted mean TP concentration in stormflow, however, was always higher than that in irrigation return flow, likely a result of sediment-associated phosphorus transport. The ratio of mean TP concentration in stormflow to that in irrigation return flow under ponded paddy conditions (1.6) was approximately one-half that under non-ponded conditions (3.1), suggesting that ponding on paddy fields played an important role in reducing soil erosion-related phosphorus export. Relationships between TN loads and stormflow runoff volumes were found except during a storm event in the high fertilization period (p