Yield–reliability analysis for rural domestic water supply from combined rainwater harvesting and run-of-river abstraction

Abstract

In many rural areas, reticulated water supply from large water resources schemes does not exist and many households obtain water from groundwater (GW), rainwater harvesting (RWH), run-of-river (ROR) flow, or combinations of these. While comprehensive yield–reliability analysis for large water resource systems is the norm, typical rural water supply analysis unrealistically aggregates data into monthly or annual time steps and does not incorporate reliability. A daily time-step simulation of household supply and frequency analysis of the number of days supplied in each year is used herein to: (a) demonstrate a realistic approach of yield–reliability analysis for RWH, ROR and combined RWH and ROR supply; and (b) show how combined utilization of the two can lead to improved supply. Integration of RWH and ROR supply has been found to improve yield and reliability substantially. The limitations of using the simpler mass curve analysis and the effect of applying a monthly time step are demonstrated.

Citation Ndiritu, J., Odiyo, J. O., Makungo, R., Ntuli, C. & Mwaka, B. (2011) Yield–reliability analysis for rural domestic water supply from combined rainwater harvesting and run-of-river abstraction. Hydrol. Sci. J. 56(2), 238–248.     

Assessment of sediment yield estimations for large watershed areas: a case study for the Seyhan,Demirköprü and Hirfanlı reservoirs in Turkey

Abstract

Analyses of data from reservoir surveys and sediment rating curves are compared to predict sediment yield in three large reservoir watershed areas in Turkey. Sediment yield data were derived from reservoir sedimentation rates and suspended sediment measurements at gauging stations. The survey data were analysed to provide the volume estimates of sediment, the time-averaged sediment deposition rates, the long-term average annual loss rates in the reservoir storage capacity, and the long-term sediment yield of the corresponding watershed areas. Four regression methods, including linear and nonlinear cases, were applied to rating curves obtained from gauging stations. Application of the efficiency test to a power function form of a rating curve with nonlinear regression yielded the highest efficiency values. Based on the analysis of the sediment rating curves, sediment load fluxes were calculated by using average daily discharge data at each gauging station. Comparison of these two sediment yield values for each reservoir showed that the sediment yields from the suspended sediment measurements, SY_GS, are 0.99 to 3.54 times less than those obtained from the reservoir surveys, SY_RS. The results from the reservoir surveys indicate that all three reservoirs investigated have lost significant storage capacity due to high sedimentation rates.     

Estimation of temporal variation of sediment yield using GIS / Estimation de la variation temporelle de l'exportation sédimentaire grâce à un SIG

Abstract

A GIS-based method is proposed for computation of temporal variation of sediment yield during isolated storm events. Data from three Indian catchments, namely Karso and Nagwa in Jharkhand and Kharkari in Rajasthan, have been used. The Integrated Land and Water Information System (ILWIS) GIS package was used for (a) catchment discretization into cell areas using grid networks, (b) evaluation of the spatial variation in catchment topographical characteristics and land use, and (c) presentation of the results obtained. The process of sediment delivery from grid cells to the catchment outlet is represented by the topographical characteristics of the cells. Unit sediment graphs for the catchments are derived by translation of the sediment yield from the grid cells and routing through a linear storage reservoir. The proposed method is found to provide satisfactory estimates of the temporal variation of sediment yield during isolated storm events. The total sediment yield of a storm event may also be computed using the proposed method.     

The impact of upstream water abstractions on reservoir yield: the case of the Orós Reservoir in Brazil

Abstract

Water abstraction for irrigation upstream of a reservoir and its impact on reservoir yield and reliability are studied. Water demand and availability are strongly related in semi-arid environments where the irrigation sector is responsible for a large part of consumptive water use. Variations in water abstractions for irrigation depend on irrigation requirements per hectare and the size of the irrigated area. The Orós Reservoir in semi-arid Northeast Brazil has been taken as a case study. The results show that water abstracttion for irrigation is of significant importance for reservoir yield and reliability. Yield—reliability simulations for the study area show that taking into account upstream water abstraction for a reservoir yield of 20.0 m³/s results in a water-scarcity probability of 10% on an annual basis (90% reliability). This is only 5% if up-stream abstraction for irrigation is ignored. This study shows that observed land-use changes in the study area do have a significant impact on reservoir yield reliability. The variability of upstream water abstraction was found to be of low importance for reservoir yield and reliability.     

Announcements

Abstract

This paper investigates for a 25-year period the sediment distribution in a semi-arid Brazilian basin (2 × 10⁴ km²) with a network containing more than 4000 surface reservoirs. The methodology is based on rating curves and fitted parameters derived from field data. The results showed that suspended load corresponded to 70% of the total sediment yield (148 t km^-2 year^-1). The relatively low contribution of the suspended load (compared with other semi-arid regions) was attributed to the impact of the numerous upstream reservoirs, which retained 235 t km^-2 year^-1. The micro (<1 hm³), small (1–10 hm³), medium-sized (10–50 hm³), and large or strategic (>50 hm³) reservoirs responded to, respectively, 5, 17, 30 and 48% of the total sediment retention by the reservoir network. This indicates that retention in the non-strategic reservoirs has a positive impact on water availability, since siltation of the strategic reservoirs would be expected to more than double if only such reservoirs existed.

Citation Lima Neto, I. E., Wiegand, M. C. &; de Araújo, J. C. (2011) Sediment redistribution due to a dense reservoir network in a large semi-arid Brazilian basin. Hydrol. Sci. J. 56(2), 319–333.     

Predicting agricultural drought in eastern Rajasthan of India using NDVI and standardized precipitation index

In the present study, prediction of agricultural drought has been addressed through prediction of agricultural yield using a model based on NDVI-SPI. It has been observed that the meteorological drought index SPI with different timescale is correlated with NDVI at different lag. Also NDVI of current fortnight is correlated with NDVI of previous lags. Based on the correlation coefficients, the Multiple Regression Model was developed to predict NDVI. The NDVI of current fortnight was found highly correlated with SPI of previous fortnight in semi-arid and transitional zones. The correlation between NDVI and crop yield was observed highest in first fortnight of August. The RMSE of predicted yield in drought year was found to be about 17.07 kg/ha which was about 6.02 per cent of average yield. In normal year, it was 24 kg/Ha denoting about 2.1 per cent of average yield.     

河北灵寿县变质岩区大理岩系赋水规律分析

河北灵寿县山丘区是太行山前典型的严重缺水地区。在该区广泛分布的片岩、片麻岩等变质岩的富水性一般较差。对变质岩区大理岩系地下水赋存规律的分析可以更好地指导和帮助当地群众解决长期面临的缺水问题。分析结果表明:该区主要存在三种大理岩含水岩组类型和两种蓄水构造类型;地下水水化学类型为Ca-HCO3型水,水质符合国家饮用水标准。     

Effect of hysteretic smoothness on inelastic response spectra with constant‐ductility

This paper presents an efficient methodology for computing constant‐ductility inelastic response spectra. The computation of constant‐ductility spectra involves numerical root‐finding algorithms to find the strongest structure providing a desired ductility response. Smooth inelastic structural behavior is modeled using a first‐order nonlinear differential equation and the transient structural response is solved using an implicit algorithm requiring Newton iterations at each time step. For structural models with smooth hysteretic behavior (not piece‐wise linear), a simple root‐finding method involving a combination of hyperbolic fits, linear interpolation, and Newton's method converges upon the highest strength (conservative) solution with a small number of iterations. The effect of the hysteretic smoothness on the occurrence of multiple roots is examined for two near‐fault and two far‐fault earthquake records, and for two measures of ductility and for normalized hysteretic energy. The results indicate how the smoothness of the hysteretic behavior affects ductility demand and constant‐ductility response spectra. Copyright © 2010 John Wiley & Sons, Ltd.     

内蒙古半拉山钼矿LA-ICP-MS锆石U-Pb与辉钼矿Re-Os年龄及其成矿动力学背景

内蒙古阿鲁科尔沁旗半拉山钼矿床位于大兴安岭南段,是新发现的中型爆破角砾岩型钼矿床.半拉山钼矿区内流纹岩围岩和花岗斑岩岩脉的LA-ICP-MS锆石U-Pb年龄分别是(157.5±3.3)Ma和(126.3±2.1)Ma,而辉钼矿样品的Re-Os同位素等时线年龄为(136.1±6.6)Ma(MSWD=0.42),表明成矿作...     

上覆压力及排水条件对吹填软土强度影响

吹填土由于其成分来源及沉积环境不同,性质千差万别。以天津海积软土为土质材料,模拟现场吹填环境,研究了吹填软土强度形成影响因素。试验表明,不同的压力及排水条件对吹填软土强度增长影响较大。当排水条件有利于土体中的水排出时,强度增长明显。上覆压力对土体强度增长的影响通过一定的排水条件得以实现,排水条件差和压力增大时,强度增长缓慢且很小,反之,强度增长快且绝对值大。