Investigation of Groundwater Quality with Borehole Depth in the Basin Granitoids of the Ashanti Region of Ghana

The dependence of groundwater quality on borehole depth is usually debatable in groundwater studies, especially in complex geological formations where aquifer characteristics vary spatially with depth. This study therefore seeks to investigate the relationship between borehole depth and groundwater quality across the granitoid aquifers within the Birimian Supergroup in the Ashanti Region. Physicochemical analysis records of groundwater quality data were collected from 23 boreholes of public and private institutions in the Ashanti Region of Ghana, and the parametric values of iron, fluoride, total hardness, pH, nitrate, and nitrite were used to study the groundwater quality-depth relationship. The results showed that the depth-to-groundwater quality indicated a marginal increase in water quality in the range of 30 to 50 m, which is mathematically represented by the low-value correlation coefficient (r2 = 0.026). A relatively significant increase occurs in the depth range of 50 to 80 m, which is given by a correlation coefficient of r2 = 0.298. The mean percent parameter compatibility was 74%, 82%, 89%, and 97% at 50, 60, 70, and 80 m depths, respectively. The variations in groundwater quality per depth ratio ranged from 1.48, 1.37, 1.27, and 1.21 for 50, 60, 70, and 80 m depth, respectively. The recommended minimum borehole depth for excellent groundwater quality is suggested with a compatibility per meter depth ratio of 1.37. This results in a range between 50 and 70 m as the most desirable drilling depth for excellent groundwater quality within the granitoids of the Birimian Supergroup of the Ashanti Region in Ghana.

Validation of TRMM and FEWS Satellite Rainfall Estimates with Rain Gauge Measurement over Ashanti Region, Ghana

Satellite rainfall estimates have predominantly been used for climate impact studies due to poor rain gauge network in sub-Saharan Africa. However, there are limited microscale studies within the sub-region that have assessed the performance of these satellite products, which is the focus of the present study. This paper therefore considers validation of Tropical Rainfall Measuring Mission (TRMM) and Famine Early Warning System (FEWS) satellite estimates with rain gauge measurements over Ashanti region of Ghana. First, a consistency assessment of the two gauge data products, the Automatic Rain Gauge (ARG) and Ghana Meteorological Agency (GMet) Standard Rain Gauge (SRG) measurements, was performed. This showed a very good agreement with correlation coefficient of 0.99. Secondly, satellite rainfall products from TRMM and FEWS were validated with the two gauge measurements. Validation results showed good agreement with correlation coefficients of 0.6 and 0.7 for TRMM and FEWS with SRG, and 0.87 and 0.86 for TRMM and FEWS with ARG respectively. Probability Of Detection (POD) and Volumetric Hit Index (VHI) were found to be greater than 0.9. Volumetric Critical Success Index (VCSI) was 0.9 and 0.8 for TRMM and FEWS respectively with low False Alarm Ratio (FAR) and insignificant Volumetric Miss Index (VMI). In general, relatively low biases and RMSE values were observed. The biases were less than 1.3 and 0.8 for TRMM and FEWS-RFE respectively. These indicate high rainfall detection capabilities of both satellite products. In addition, both TRMM and FEWS were able to capture the onset, peak and cessation of the rainy season, as well as the dry spells. Although TRMM and FEWS sometimes under/overestimated rainfall, they have the potential to be used for agricultural and other hydro-climatic impact studies over the region. The Dynamic-Aerosol-Cloud-Chemistry Interactions in West Africa (DACCIWA) project will provide an improved spatial gauge network database over the study area to enhance future validation and other climate impact studies.

加纳阿善堤地区农户参与稻田项目的决定因素研究

本文对加纳阿哈福阿诺南区（Ahafo Ano Southdistrict）农户参与稻田项目的决定因素进行研究。稻田项目的实施，主要基于加纳稻米消费的扩张，导致了对生产自给的需求。为此，日本的一些机构在加纳的较低洼地区引入了稻米的生产。当然，在参与稻田项目的全部三阶段（1997—2001，2002—2004和2004—2009）的农户中，也存在着不同的问题。因此，在前两个阶段结束和第三个阶段接近完成的情况下，研究农户参与稻田项目的决定因素，从而促进项目逐步完善就显得尤为重要。由于稻田开发项目主要集中在阿哈福阿诺南区，这一地区分布有主要的流域，因此，本研究也主要在此地区进行。受访者主要从5个村庄中随机抽取，这5个村庄涵盖了项目的所有3个阶段，共选取了225名农民，通过结构式问卷调查方式搜集了相关资料。论文运用描述性统计方法分析了样本农民的社会经济特点，同时运用Probit模型对影响农户参与稻田项目的决定因素进行了研究。结果表明，样本中多数农民为50岁以下男性，他们具有较高的教育水平，同时信奉基督教，但他们在低地种植水稻的经验不到5年，水稻种植面积不到5英亩，约有61％的接受访问者每户有5至10人，样本中参与项目的人数少于没有参加项目的人数。从Probit模型的结果来看，确定模型拟合度的卡方值在1％的统计水平上显著，“参与稻田项目的持续性”（t=5．02）和“村庄稻田项目的起始时间”（t=-1．53）两变量分别在5％和10％的统计水平上显著。从文中也可以看出，在引进稻田项目的同时，也引进了适当的田间管理和水资源管理。为了确保农民参与稻田项目的可持续发展，也有必要对论文中基于项目3阶段分析所揭示的重要的社会变量给予政策上的重视。