Experiences and lessons learned from interventions in the Lake Victoria Basin: The Lake Victoria Environmental Management Project

The Lake Victoria basin has experienced a myriad of environmental changes leading to its degradation, and necessitating various interventions to be implemented. The purpose of this study was to review early development initiatives, past and ongoing interventions in order to document experiences and lessons learned from them. The methods used in this study include review of published articles, project reports, and personal opinions of experts and project implementers in the lake basin. There are numerous threats to the lake basin, the major ones being poor land use and agricultural practices, catchment deforestation, destruction of wetlands, pollution loading, fishing malpractices and invasion by exotic aquatic weeds. These threats have resulted in rampant land and wetland degradation, leading to poor water quality and consequent water loss, a decline in the diversity of the commercial fisheries, and the lake’s biodiversity in general, unsustainable use of natural resources, increased poor human health and food insecurity, with high levels of poverty among the riparian communities. Initiatives for socio‐economic development within the lake basin began as early as the turn of the 20th century, while intervention studies started as early as the 1920s. Current lake management intervention projects, such as the Lake Victoria Environmental Management Project (LVEMP), undertaken by the riparian states of the East African Community, have invested heavily in the lake basin, with the goal of addressing the above‐noted threats to the lake. Some pilot projects undertaken through the LVEMP include: (i) water quality and quantity monitoring; (ii) industrial and municipal management; (iii) fisheries studies; (iv) water hyacinth control; (v) wetlands; (vi) land use; (vii) catchment afforestation; and (viii) micro‐projects to alleviate poverty, to cite a few examples. Phase 1 of the LVEMP was a major effort in the history of the lake basin; hence, its critical examination. To this end, this study highlights, in chronological order, the experiences, achievements, challenges and lessons learned with regard to Phase 1 of the LVEMP.     

Pollution of Winam Gulf, Lake Victoria, Kenya: A case study for preliminary risk assessment

A preliminary risk assessment was undertaken on the Kenyan part of Lake Victoria to identify the major causes of degradation of water quality. Urban, industrial and agricultural loads were quantified and related to geographical and climatic conditions. A few analyses of persistent contaminants were carried out on fish. Monthly limnological investigations were conducted together with river water quality analyses. Phosphorus loads and consequent eutrophication were identified as the major causes of water quality degradation.     

Risk assessment for organochlorines and organophosphates pesticide residues in water and Sediments from lower Nyando/Sondu‐Miriu river within Lake Victoria Basin,Kenya

The objective of this study was to survey and document pesticide residue levels in the lower Nyando/Sondu‐Miriu catchment areas of Lake Victoria, Kenya, during the dry and rainy seasons of 2009. Water and sediment samples from the Nyando/Sondu‐Miriu Basin were analysed for selected pesticide residues, using gas chromatography equipped with Ni⁶³ and CP‐SIL 8CB‐15m and TSD detectors for organochlorine and organophosphorus pesticide residues, respectively. The findings indicated that banned organochlorines are still being used in the catchment. Dieldrin and p,p′‐DDD were notably higher (P < 0.05) in concentrations than their metabolically formed analogues of aldrin and DDT, respectively. Notably, organophosphorus was below detection levels in water samples, whereas diazinon and malathion were at higher levels in sediment samples. The total residues of DDT, HCH, methoxychlor and endrin generally were below WHO drinking water limits of 2, 2, 20 and 0.01 μg L^?1, respectively, whereas aldrin and dieldrin were above the recommended values of 0.03 μg L^?1. Agricultural activities in the Lake Victoria Basin are influencing accumulation of the pesticide residues in the basin rivers and the lake. The study recommends creation of buffer zones around the natural water bodies to reduce the inflow of pesticides into water bodies. An integrated pest management approach that encourages reduced usage of chemical compounds also should be encouraged.     

Water Balance of the Upper Jordan River Basin

Sharing water in the Jordan basin has been a key topic in the recent peace talks between Israel and its neighbors. Knowing the quantity of water available is a prerequisite to water sharing. Many different values have been published in recent years. Different sources report Jordan's discharge flow into Lake Kinneret anywhere from 460 to 800 Mm³/year. The aim of this article is to present a water balance for the Jordan basin for a 15-year period. The years 1977–1978 to 1991–1992 were studied for the basin's water budget, as they represent the present day (1998) land use. The results show that Lake Kinneret has a yearly average input (= output) of 770 Mm³. Israel uses some 800 Mcm³/year from the entire Jordan basin, of which 440 Mm³ is used within the basin and the rest outside. There is about 100 Mm³ for future utilization in the watershed. The yearly Jordan's discharge to the Dead Sea is 220–250 Mm³. Reporting by various secondary data sources is compared to primary data findings to illustrate the great variability of data reporting and to provide annual flow estimates, based largely on primary sources, for the Upper Jordan River.     

近40年鄱阳湖水位变化趋势

利用实测水位资料,分析鄱阳湖水位近40年中的变化趋势,并用倾向率作定量描述。结果表明,鄱阳湖年最高水位以0.22m/10a的倾向率上升,其出现时间以3.2d/10a的倾向率推迟,大洪水年以0.06a/10a的倾向率增多,洪水位升高与大洪水增多使得洪涝灾害加剧,将成为鄱阳湖区开发整治中的突出问题。     

Biogeochemical characterization,phosphorus sources and intrinsic drivers to its speciation within the Nyanza Gulf of Lake Victoria

Lake Victoria, like many African great lakes, was formed through tectonic activity that formed East African Rift Valley. The lake's ecology has undergone dramatic reorganization dating back to the 1920s, before agricultural mechanization and high urban populations were observed, transforming from it from a desirable to less desirable state. The present study was conducted to better understand Nyanza Gulf's biogeochemical characteristics, phosphorus sources and the driving forces to their speciation. Five littoral‐limnetic‐littoral transects were sampled for water‐associated phosphorus (soluble reactive phosphorus, SRP; total phosphorus, TP_W); sediment‐associated phosphorus (non‐apatite inorganic phosphorus. NAIP); apatite phosphorus, AP; inorganic phosphorus, IP; organic phosphorus, OP; total phosphorus, TP_S); elemental compositions (calcium, Ca; iron, Fe; aluminium, Al; manganese, Mn); organic matter (OM); and organic carbon (OC) contents in the sediment. The SRP and TP_W concentrations ranged from 22.9 to 142.9 μg/L, and 57.1 to 277.1 μg/L, respectively. The littoral sampling sites exhibited relatively higher TP_W concentrations than the limnetic sites. Sheltered bays and sites located off sewerage discharge points had higher NAIP concentrations exceeding 400 mg/kg, compared with strong current areas. The AP and TP_S concentrations ranged from 136.7 to 1,511.3 mg/kg, and 512.5 to 2,254.4 mg/kg, respectively. The AP and TP_S concentrations were generally higher (>500 mg/kg) within the littoral zones compared to the limnetic zones; with the littoral sites located close to documented carbonatite rock substrates manifesting exceptionally high concentrations. Nyanza Gulf's eutrophic/hypertrophic status is derived highly from shoreline erosions of phosphorus‐enriched carbonatite rocks associated with rift valleys and from municipal sewerage discharges. Re‐afforestation, fringing wetland restorations and tertiary treatment of municipal waste waters are vital for its ecological restoration.     

A review on the status of some major fish species in Lake Victoria and possible conservation strategies

Lake Victoria, the second largest freshwater lake in the world, supports an enormous flora and fauna biomass, with a large human population around the Lake. The lake is a source of food (fish), water for domestic use and crop and livestock production, transportation and tourism, among other uses. As a result of these varied uses, human intervention within the lake and its catchment has resulted in several ecological changes in the lake in recent years, with profound effects on its fish resources. One of the most notable changes is the reduction and risk of extinction of some fish species, including the endemic tilapiine species (Oreochromis esculentus and Oreochromis variabilis), catfishes (Xenoclarias eupogon), haplochromines and cyprinids (Labeo victorianus and Barbus altinialis) in the lake. The reduced biodiversity, as well as extinctions within the lake, has been attributed to the introduction of alien fish species (e.g. Nile perch (Lates niloticus) and Nile tilapia (Oreochromis niloticus) into the lake, habitat loss and cultural eutrophication. If left unchecked, these changes will have devastating effects on the lake's resources, as well as to people living around the lake and beyond who depend on the lake fisheries for their livelihood. Thus, there is an urgent need for management measures based on sound scientific research to be implemented in order to curb the loss of ichthyodiversity within the lake, as well as to save the livelihoods of those stakeholders who are either directly or indirectly dependent on the lake.     

Exotic introductions to the fishery of Lake Victoria: What are the management options?

Lake Victoria is Africa's most important source of inland fishery production, exhibiting annual catches of ≈ 400 000 mt. The predatory Nile perch, Lates niloticus, and the herbivorous tilapiines, Oreochromis niloticus, Oreochromis leucostictus, Tilapia zillii and Tilapia rendalii, were introduced in Lake Victoria in the 1950s and 1960s. Nile perch were introduced to convert the abundant, but bony, haplochromines to fish flesh, while the tilapiines were introduced to boost the declining fishery. Since that time, the fisheries of Lake Victoria have undergone dramatic social and ecological changes. The catches increased tremendously, changing the fishery from artisanal to commercial, in turn increasing fisher income and employment opportunities. However, there was a decline and, in some cases, the disappearance of many indigenous fish species, especially the haplochromine cichlids. This reduction was attributed to overexploitation, predation, and competition and hybridization with the introduced species. The decline of the native fish species has had impacts on the trophic and ecological status of the lake. Nile perch now dominate the formerly complex food web. The loss of phytoplanktivorous haplochromines has contributed to an increase in algal blooms, reduction in water quality and occasional fish kills. Water hyacinth, Eichhornia crassipes, invaded Lake Victoria in 1988, with high rates of infestation in shallow waters and bays, which are breeding and nursery grounds for most fish species. Catches of Nile perch decreased following the infestation, while those of Nile tilapia, lung fish (Protopterus aethiopicus) and mud fish (Clarias gariepinus) increased. Haplochromines species also showed some signs of recovery. In view of all these changes, the future of the Lake Victoria fishery is uncertain.     

简述乌伦古湖入湖水量及湖水位情势分析

由于乌伦古河河川径流具有连续枯水年且枯水时段长的特点,且乌伦古河在连续枯水年份出现断流是一种不可抗拒的自然因素,需要在流域综合规划指导下,具体研究吉力湖和布伦托海入湖水量及水位变化情势,尽可能恢复乌伦古河流域原有生态,保障洄游性鱼类所需要的流量要求,显著减少布伦托海湖水向吉力湖倒灌发生的时间和倒灌水量,使乌伦古湖和周边生态系统有所好转。     

浅析太湖流域水问题及对策

随着流域社会经济的发展，太湖流域的水问题日益突出，主要是防洪标准的提高跟不上社会经济的刀菜，水污染造成的水质型缺水日趋严重、水资源管理无序。解决问题的对策是进一步完善防洪除涝设备、实施水资源统一管理和建立新型的流域管理体制，并建立太湖流域水调度管理中心，实现太湖流域水利现代化，使太湖流域水利与流域经济、社会、环境协调发展。     

调节鄱阳湖枯水位 维护江湖健康

2003年以来,鄱阳湖枯水期水位连创新低,持续时间延长,导致水质恶化、湿地生态系统遭受破坏、候鸟栖息地受到威胁;生产生活用水、农田灌溉、航运和水产捕捞受到严重影响．为了改变鄱阳湖枯水期持续处于低水位状态,确保江湖水系健康,提出了鄱阳湖枯水调节的基本原则：改善生态环境为主要目的,调枯不调洪;从整体出发,做到江湖两利;以简单工程进行调节,趋利避害;保持工程运用的灵活性,实施适应性管理．同时,规划了鄱阳湖枯水调节工程的地点、规模和运行方式．作为一个以保护和改善生态环境为主的水利工程,其具有改善水环境、保护水生态、维护水安全,保护鄱阳湖湿地的生态环境及确保候鸟越冬条件,缓解长江下游枯水期低水位状态和促进湖区经济社会发展等方面的效益．     

白洋淀流域气象要素和人类取用水变化过程分析

白洋淀是华北地区最大的淡水湖泊,但是近年来频繁出现干淀问题,正确分析其主要原因为制定白洋淀入淀水量保障措施具有至关重要的意义。采用Mann-kendall方法对白洋淀历史降水、气温及农业、工业生活用水量的变化过程进行分析。结果显示,流域内山区与平原区降雨量均呈现减小趋势,且山区的降水衰减程度大于平原区降水;流域内1980年以后气温呈现增加趋势;用水方面,除农业用地表水在20世纪90年代后呈减少趋势,其他用水均为持续显著增加趋势,其中农业用地下水占据所有用水比例较大。上述结果表明,降水不断减少、气温持续升高以及人类活动强度的逐步加大是造成白洋淀入淀水量减少的主要原因。     

Some aspects of the biology and life‐history strategies of Oreochromis variabilis (Boulenger 1906) in the Lake Victoria Basin

Oreochromis variabilis (Boulenger), a fish species endemic to Lake Victoria, was abundant, forming an important component of the indigenous fisheries stocks before and up to the late‐1950s. Catches declined drastically thereafter, and only sporadic catches are currently found in Lake Victoria. Remnants population of the species, however, are found in several small waterbodies (SWBs) within the lake basin. The life‐history characteristics of O. variabilis in Lake Victoria, including, sex ratio, reproduction and length–weight relationship, were compared to those in selected three SWBs in the lake basin. Fish samples were collected by monofilament gillnets of 30–255 mm between 2001 and 2005. Males predominated over females from all the sampled sites (sex ratio 1.00:0.33). Length at first maturity (Lm₅₀) had mean (±SE) of 18.48 ± 1.50 cm TL for males, and 16.87 ± 0.95 cm TL for females, and did not exhibit any significant differences between habitats. Fecundity ranged between 73 and 14 800 eggs for fish of 13.5–18.6 cm TL, respectively. Absolute fecundity of O. variabilis was proportional to the body weight, but nearly proportional to the cube of the fish length. Egg diameter varied from 0.3 to 5.19 mm, with a mean (±SE) of 3.44 ± 0.08 mm. Growth was allometric in both male and female, being significantly different from the expected value of 3 (P < 0.05). The life‐history strategy of O. variabilis is discussed within the context of changes in the lake and the SWBs.     

Seasonal variations of phytoplankton species in Lake Victoria and the influence of iron and zinc ions on the dominant species identified during 2006–2007 studies

The current study was conducted for 2 years (2006 and 2007) during January, April and September to investigate seasonal variations in biological parameters and planktonic biodiversity observed at four sampling sites (MRM, M500, SRM and S500) in Lake Victoria. Blue‐green algae (Cyanophyta) dominated the lakeshore waters of Lake Victoria, comprising 54.1% of the total algal content, compared to 24.4% for diatoms and 14.7% for green algae (Chlorophyta). Euglenophytes and dinoflagellates both constitute <10% of the algal biomass. The algal distribution at the Sango Bay sampling sites, however, is different in that it is dominated by diatoms, in contrast to Murchison Bay, which was dominated by blue‐green algae. This study also investigated the influence of iron (Fe²⁺and Fe³⁺) and zinc (Zn²⁺) ions on four strains of microcystis (CYN 464, CYN 465, CYN 478 and CYN 522) isolated from Murchison Bay in Lake Victoria. The suggestion that iron species and zinc ions might limit phytoplankton growth in Lake Victoria was tested by enriching algal culture media with different metal concentrations. Based on measurements of the algal biomass of four species of Lake Victoria, the algal biomass of the four microcystis strains generally decreased with increased zinc and Fe²⁺ concentrations. The algal biomass of the four strains, however, increased with increased Fe³⁺ concentrations. This response to different metal concentrations provides evidence that high Zn²⁺ and Fe²⁺ ion concentrations limit phytoplankton growth and species distribution. The availability of Fe³⁺ ions is an important selective force on Lake Victoria phytoplankton communities.     

Lake-Level Change and Water Balance Analysis at Lake Qinghai,West China during Recent Decades

Lake Qinghai, the largest saline lake with an area of 4,260 km² (2000) and average depth of 21 m (1985) in West China, has experienced severe decline in water level in recent decades. This study aimed to investigate water balance of the lake and identify the causes for the decline in lake level. There was a 3.35-m decline in water level with an average decreasing rate of 8.0 cm year⁻¹ between 1959 and 2000. The lake water balance showed that mean annual precipitation between 1959 and 2000 over the lake was 357 ± 10 mm, evaporation was 924 ± 10 mm, surface runoff water inflow was 348 ± 21 mm, groundwater inflow was 138 mm ± 9 and the change in lake level was −80 ± 31 mm. The variation of lake level was highly positively correlated to surface runoff and precipitation and negatively to evaporation, the correlation coefficients were 0.89, 0.81 and −0.66, respectively. Water consumption by human activities accounts for 1% of the evaporation loss of the lake, implying that water consumption by human activities has little effect on lake level decline. Most dramatic decline in lake level occurred in the warm and dry years, and moderate decline in the cold and dry years, and relatively slight decline in the warm and wet years, therefore, the trend of cold/warm and dry climate in recent decades may be the main reasons for the decline in lake level.     

Artisanal and commercial fishing gear and practices in the Lake Victoria basin drainage systems of Kenya: A photodiagrammatic verification

This study focused on providing a photodiagrammatic database illustrating various types of fishing gear and practical skills currently used in artisanal and commercial fishing in the shoreline, nearshore and offshore areas drainage systems of Kenya in the Lake Victoria drainage basin. It also identified the fish species typically caught by the fishing gear, and the gear catch per unit effort and selectivity. Four artisanal fishing gears (spear, trap, basket and hook) and two commercial gears (mosquito seine and purse seine) are used to fish in shoreline areas. Five commercial fishing gears (gill net, parallel tennis net, semicircular‐tennis net, sett net, long line) are used to fish in nearshore areas, while two commercial gears (drift net and offshore seine net) are used in offshore areas. For artisanal fishing, the basket is the most efficient gear for catching six fish species. The mosquito seine is the most efficient commercial fishing gear for catching 22 fish species. There is evidence for a chronological shift to more efficient artisanal and commercial fisher handmade fishing gear, resulting in overexploitation of diverse fish species. At the same time, the licensing and management policies for the use of various fishing gear are unclear, suggesting re‐evaluation of policies to cater for the use of handmade fishing gear.     

基于GRACE卫星数据的汉江流域旱情反演及影响因素定量分析

气候变化和人类活动对汉江流域旱情有重要影响。利用卫星时变重力场反演地面水储量可以弥补传统流域水储量监测的缺陷。以GRACE卫星数据为基础,采用水储量亏损方法建立模型反演汉江流域2004—2014年间干旱事件,结合多源卫星数据和居民用水量数据,定量分析了气候变化和人类活动对汉江流域干旱事件的影响。结果表明,汉江流域2006、2007、2011、2013年分别发生了干旱事件,降雨、蒸发、人类活动(水库蓄水和居民用水量)等变量与陆地水储量变化显著相关,气候变化对4场干旱事件发生的贡献率分别为0.41、0.43、0.36、0.36,人类活动对4场干旱事件发生的贡献率分别为0.59、0.57、0.65、0.64,贡献度的趋势表明人类活动对汉江流域干旱事件的影响在不断增强。     

The role of the Yala swamp lakes in the conservation of Lake Victoria region haplochromine cichlids: Evidence from genetic and trophic ecology studies

Lake Kanyaboli, an isolated satellite lake of Lake Victoria, has been suggested as a potential refugium for haplochromine cichlids that have gone extinct in the main basin of Lake Victoria. Mitochondrial DNA (mtDNA) molecular markers, as well as feeding ecology studies, were employed in this study to re‐evaluate the evolutionary and ecological significance of six common Lake Kanyaboli haplochromines. The mtDNA marker revealed high genetic variability within four of the six haplochromine cichlids. Five haplotypes were discerned in Astatoreochromis alluaudi (n = 27), seven in Lipochromis maxillaris (n = 29), five in Astatotilapia nubila (n = 12) and 11 in the endangered Xystichromis phytophagus (n = 205). A haplotype genealogy suggests that Lake Kanyaboli harbours mtDNA haplotypes that could have been lost or not sampled in Lake Victoria, or could have arisen in situ. Lipochromis maxillaris appears to have undergone a recent demographic expansion. The pairwise F_STs indicated that only the comparison between X. phytophagus and A. nubila led to a non‐significant F_ST value. All other comparisons were significant at the 0.01 level, indicating the genetic distinctiveness of the haplochromines in the satellite lake. This could suggest that the lake harbours ‘pure’ relict populations of the haplochromines and therefore that Lake Kanyaboli can be considered a ‘genetic reservoir’. Gut content analysis of the six haplochromine species revealed that eight different food items were consumed. No single species fed exclusively on a single food item, but certain food items contributed higher proportions of the fish diet for each fish species. Resource partitioning therefore could be discerned within this haplochromine community. Thus, Lake Kanyaboli and similar satellite lakes provide an opportunity for conservation of both genetic and trophic diversity threatened by introduction of exotics in the Lake Victoria basin. Lake Kanyaboli should be recognized and conserved as important evolutionary significant units for Lake Victoria region haplochromine species.     

海河平原地下水储量变化的重力卫星反演和流域水量平衡

南水北调工程向华北输水与地下水压采的实施,一定程度改变了海河平原供用水格局,影响了海河平原的地下水储量。准确监测地下水储量变化是水安全保障和地下水战略储备的基础。本研究以水资源公报数据为基准,比较了重力卫星(GRACE)不同的信号处理方法和相关产品,反演了2003—2020年海河流域总水储量及其平原区地下水储量变化,分析了海河流域2000—2019年供用水结构变化和水量平衡关系,量化了总水储量变化对流域蒸散发估算的影响。结果表明：GRACE JPL Mascons数据反演的海河平原地下水储量变化与水资源公报数据的决定系数最高;2003—2020年海河平原地下水储量总体分3阶段呈下降趋势,2003—2011年、2012—2015年和2016—2020年的下降速率分别约为-23.9±1.3亿m³/a、-75.5±5.3亿m³/a、-37.3±2.6亿m³/a;在不考虑海河流域年总水储量变化条件下估算的2003—2019年多年平均蒸散量(521 mm/a),与考虑年总水储量变化的多年平均蒸散量(530 mm/a)相差约10 m...