Evaluation of Agricultural Nonpoint Source (AGNPS) model for small watersheds in Korea applying irregular cell delineation

The Agricultural Nonpoint Source (AGNPS) model was tested in two small agricultural watersheds in Korea. The model was calibrated for 412.5 ha located in the Balhan watershed. The rainfall amount distinguishing between antecedent moisture conditions (AMC) I and II was changed to calibrate the runoff volume. A validation was performed for 274.1 ha located in the Banwol watershed, with similar land use and soil characteristics as the 412.5 ha in the Balhan watershed. The input data were extracted from multiple GIS layers using the Geographic Resources Analysis Support System (GRASS)-AGNPS interface. The AGNPS model was modified to treat the undisturbed forest areas as irregular cells instead of the uniform cell division currently used by AGNPS. Simulated results from the irregular cell-based scheme (ICS) and the uniform grid scheme (UGS) of ANGPS were compared with the observed data. The ICS increased runoff volume and decreased peak flow rate and sediment yields from the watershed compared to the UGS. The ICS significantly reduced the number of cells in a watershed and provided better agreement for surface runoff and peak flow rate compared to the UGS.     

方便水库汇水区典型暴雨情况下产流产沙过程分析

研究区方便水库汇水区为苏南丘陵区典型山区性小流域,研究通过在位于入库主要河流青龙河下游设置控制站,测定暴雨侵蚀下每次小流域产流过程水沙含量,结合降雨数据。分析每次过程降雨量、产水量和产沙量之间的关系,并进一步探讨产沙总量与各项测量指标之间的相关性。结果表明：①近3年的18场暴雨中,共有7场产流产沙,主要受雨量和降雨历时影响;②小流域产流和产沙过程与降雨具有一定的一致性,降雨停止后水沙产量开始减少直至停止;③不同暴雨特性产生的水量和沙量差距较大,暴雨侵蚀下的小流域产沙模数最高可达7．85t／（km2·d）;④相关性分析发现,该小流域产沙总量与产水总量、雨量和降雨动能有一定关系,相关性系数分别为0．929、0．645和0．623。     

地表水体中多环芳烃污染的研究进展

介绍了近年来地面水体中的多环芳烃的研究进展,重点综述了国内外河流、近海海域和湖泊等地表水体中地表水和沉积物中多环芳烃的污染现状。     

坡面径流量与含沙量动态测量系统

设计了一套测量坡面径流含沙量与径流量的动态测量系统,利用γ射线穿过不同介质后强度衰减不同的规律来测量含沙量,通过检测径流注入给定容器时液位由下检测点到达上检测点的时间来测定流量。实际应用结果表明,系统工作稳定,操作方便,省工省时,测量结果准确。系统不仅适合于室内土壤侵蚀试验中含沙量与径流量的测量,而且可用于野外坡面土壤侵蚀试验小区长期定点监测和其他相关试验研究。     

Annual carbon and nitrogen loadings for a furrow-irrigated field

Evaluations of agricultural management practices for soil C sequestration have largely focused on practices, such as reduced tillage or compost/manure applications, that minimize soil respiration and/or maximize C input, thereby enhancing soil C stabilization. Other management practices that impact carbon cycling in agricultural systems, such as irrigation, are much less understood. As part of a larger C sequestration project that focused on potential of C sequestration for standard and minimum tillage systems of irrigated crops, the effects of furrow irrigation on the field C and N loading were evaluated. Experiments were conducted on a laser-leveled 30 ha grower's field in the Sacramento valley near Winters, CA. For the 2005 calendar year, water inflow and runoff was measured for all rainfall and irrigation events. Samples were analyzed for C and N associated with both sediment and dissolved fractions. Total C and N loads in the sediment were always higher in the incoming irrigation water than field runoff. Winter storms moved little sediment, but removed substantial amounts of dissolved organic carbon (DOC), or about one-third of the total C balance. Despite high DOC loads in runoff, the large volumes of applied irrigation water with sediment and DOC resulted in a net increase in total C for most irrigation events. The combined net C input and N loss to the field, as computed from the field water balance, was 30.8 kg C ha⁻¹ yr⁻¹ and 5.4 kg N ha⁻¹ yr⁻¹ for the 2005 calendar year. It is concluded that transport of C and N by irrigation and runoff water should be considered when estimating the annual C field balance and sequestration potential of irrigated agro-ecosystems.     

Land reclamation using reservoir sediments in Tigray,northern Ethiopia

Accelerated soil erosion leads to sedimentation in reservoirs and a decline in their life span. As many reservoirs in northern Ethiopia are dry at the end of the dry season, we were able to evaluate the potential of using reservoir sediments for land reclamation. Stripped land from which construction material for the reservoirs had been excavated was covered with 0, 15 and 30 cm of sediment and planted with a local garlic cultivar (Allium sativum). The applied reservoir sediments had low to medium organic C and total N contents and were high in available P and exchangeable cations. The yield of garlic increased with additional available water and the application of sediments. The results show that total biomass and bulb yield were three times higher on the reclaimed plots than on the control ones (11.7 t/ha vs. 3.6 t/ha for the biomass; 7.7 t/ha vs. 2.0 t/ha for the yield). When sediment transport and labour costs were taken into account, plots with 15 cm of sediments had in the first cropping season a cost‐benefit ratio of 3, whilst those with 30 cm had a cost‐benefit ratio of 0.9. This study demonstrates that the use of relatively small quantities of reservoir sediments is an economically viable strategy for land reclamation. The result can be improvement in income for resource‐poor farmers by as much as 76%, and the life expectancy of the reservoirs is also increased.     

Is MUSLE apt to small steeply reforested watershed?

The reforested headwater watersheds in Japan are very important from the points of view of commercial and environmental aspects. At the present time, much and varied research is running to assess and understand the hydrologic behavior of these watersheds. The present study was conducted to evaluate the applicability of the deterministic model MUSLE in the Mie small steeply reforested watershed. The model was tested and calibrated using accurate continuous suspended sediment data collected during eight storm events in 2004. Results of the original model simulations for storm-wise sediment yield did not match the observed data, while the revised version of the model could imitate the observed values well. The results of the study approved the efficient application of the revised MUSLE in estimating storm-wise sediment yield in the study area with a high level of agreement of beyond 88%, an acceptable estimation error of some 14% and non-significant difference in mean values.     

滇池沉积物金属污染及潜在生态风险研究

对滇池126个采样点沉积物0～5 cm、5～10 cm和10-20 cm中Cu、Zn、Pb、Cr、Cd、Hg和As等7种金属的含量进行了分析测定,各金属含量测定结果均高于相应的参比值,表明滇池沉积物受到了不同程度的金属污染.各金属含量的水平分布很不均衡,Zn、Pb、Cd、Hg和As含量随沉积物深度的减小而增大,Cu和Cr含量则随沉积物深度减小而减小,表明滇池沉积物中Cu和Cr污染整体上出现了减缓的趋势,而Zn、Pb、Cd、Hg和As污染在不断加剧.用H(a)k(a)nson潜在生态风险指数对滇池沉积物金属污染的生态风险进行了分析,结果表明:滇池沉积物存在轻微的Cu、Zn、Pb、Cr和As污染生态风险,以及中等的Hg和Cd污染生态风险;全湖沉积物金属污染的平均生态风险指数RI值为205.03,属中等生态风险,但有快速加大的趋势.     

大青山不同植被类型保育土壤能力

采用人工模拟降雨的方法研究了不同植被类型枯落物层和土壤层对降雨产流量的阻滞作用,从而揭示其保育土壤的能力。结果表明:在0.80～0.85 mm/min降雨强度下,不同植被类型的产沙量由大到小依次为,未封育荒草坡、油松幼龄林、已封育荒草坡、油松中龄林、虎榛子阳坡灌丛、白桦幼龄林、白桦中龄林、油松近熟林、虎榛子阴坡灌丛、白桦近熟林;在0.60～0.65 mm/min降雨强度下则为,未封育荒草坡、油松幼龄林、已封育荒草坡、白桦幼龄林、油松中龄林、虎榛子阳坡灌丛、虎榛子阴坡灌丛、油松近熟林、白桦中龄林、白桦近熟林。同一植被类型枯落物层、土壤层滞水量及保土能力均与模拟降雨强度呈反比,不同植被类型保育土壤能力由大到小为,白桦天然次生林、油松人工林、虎榛子灌丛、荒草坡。     

旅游活动对洞穴生态环境的影响分析

通过查阅有关文献资料,并结合所监测的重庆雪玉洞洞穴生态环境,分析认为:旅游活动使得洞穴CO2含量呈升高趋势,洞穴温度也呈升高趋势且变幅增大,洞穴空气湿度呈降低趋势,还可能破坏洞穴生态系统,这对洞穴碳酸盐岩沉积物的保护十分不利,应引起人们足够的重视。此外,旅游活动很容易恶化地下河水的水质,威胁岩溶区的饮水安全。