三角洲对人类社会和滨海生态系统都具有非常重要的作用。然而，为了满足人类的需要，越来越多的人类活动，如水坝调度等，已经影响了三角洲的地貌演变。Volta河是Volta河三角洲（VRD）的主要泥沙来源，Akosombo（1964年竣工）和Kpong（1982年竣工）大坝对Volta河进行了大量的调节，导致其三角洲的地貌演化产生了负面的影响。因此，有必要就水坝调度对水文变化的影响程度以及水文变化如何进一步影响VRD的地貌演变，特别是三角洲面积和海岸线的变化，开展研究。 本研究首先利用加纳Volta河管理局和加纳科学与工业研究理事会水资源研究所提供的1936至2018年Volta河的月均和年均入海径流量、输沙量数据（分别表示为Qw和Qs）进行了水文变异分析。本研究采用简单回归分析和MK趋势分析方法，对Akosombo大坝建设前后的入海径流量、输沙量的年际变化进行了分析。进一步计算了Akosombo大坝建设前（1936-1964）、Kpong大坝建设前（1970-1982）和Kpong大坝建设后（1983-2018）不均匀系数（Cy）和调节系数（Cr），以分析水坝调度年内入海径流量、输沙量的变化。 同时为了开展三角洲地貌演化分析，本研究从美国地质勘探局下载了1972年至2018年期间可用的陆地卫星遥感图像。使用Envi Classic软件中的镶嵌工具箱，将包括研究区域（Volta河三角洲）的两个区域的遥感图像，即路径193、第56行和路径193、第56行的遥感影像，进行合并。对于MSS遥感影像和TM/ETM遥感影像，本研究分别使用432波段和543波段的伪彩色图像，利用ArcGis 10.3人工划定海岸线并计算三角洲面积。计算了三角洲侵蚀-堆积随时间的变化，并分析其与河流累积输沙量的关系。 大坝建设前的年平均入海径流量为1237 m3/s，输沙量为5.9×105 m3/d，其标准差分别为516.8 m3/s和2.48 ×105 m3/d；大坝建设后年平均流量为949 m3/s，输沙量为4.6×104 m3/d，其标准差分别为196.1 m3/s和0.94×104 m3/d。年入海径流量和输沙量的下降率分别为23.23%和92.3%。年内径流量不均匀系数在Akosombo大坝建设前、Kpong大坝建设前和Kpong大坝建设后的三个时期内分别为1.45、0.07和0.09；年内径流量调节系数则分别为0.55、0.03和0.04。年内输沙量不均匀系数在Akosombo大坝建设前、Kpong大坝建设前和Kpong大坝建设后不均匀系数分别为1.44、0.04和0.09；年内输沙量调节系数分别为0.55、0.03和0.04。水文分析结果显示，建坝前年际和年内的径流量和输沙量的变异程度均大于建坝后，Akosombo大坝的建设对年内径流量和输沙量的影响远大于Kpong大坝。 与早期有关三角洲海岸线侵蚀的研究报道相比，本研究的结果表明，尽管三角洲的局部岸线存在侵蚀和堆积的波动，但整体海岸线比较稳定（面积最大变化率仅为0.56%）。三角洲面积变化和河流累积输沙量的关系分析显示两者的相关性较弱，表明河流输沙量对现代Volta河三角洲的演变影响很小。因此，本研究表明，早期的Volta河三角洲面积（1970年代以前）由于河流输沙量的减少发生了剧烈的侵蚀，但是随着时间的推移， Volta河三角洲在1970年代后已经达到了某种程度的平衡状态。如果Volta河输沙量保持在现在的水平，Volta河三角洲在未来将继续保持稳定。 本研究分析了水坝调度对Volta河水文变异及其对三角洲地貌演化的影响，可为Volta河未来的开发以及Volta河三角洲的保护提供科技支撑。同时，本研究可为世界上类似三角洲的演化，如中国的黄河三角洲，提供了借鉴意义。随着黄河入海泥沙的持续降低，未来黄河三角洲可能逐渐进入蚀退阶段，并最终达到三角洲面积演化的稳定状态。

Deltas are important to both human societies and coastal ecosystems. However, increasing anthropogenic activities to meet human needs, such as dam regulations, have affected the morphological evolution of deltas worldwide. The Volta River, the main sediment source for the Volta River Delta (VRD), is greatly regulated by the Akosombo dam (completed in 1964) and the Kpong dam (completed in 1982), which leads to adverse effects on the morphological evolution of the Volta River Delta. Therefore, it has become necessary to investigate the extent of the impact of the dam regulations on the hydrological alterations and how the hydrological alterations subsequently influence the morphological evolution of VRD especially the delta area and shoreline changes. The research first analyzed the hydrological alteration using monthly and annual river and sediment discharges (Qw and Qs respectively) from 1936 to 2018, which were obtained from the Volta River Authority of Ghana and Water Resources Institute of the Council for Scientific and Industrial Research of Ghana. The inter-annual variations for pre- and post- Akosombo dam were analyzed using simple regression and MK trend analysis. For intra-annual variations, the non-uniformity coefficient (Cy) and the regulated coefficient (Cr) were determined for the pre- Akosombo (1936 to 1964), The pre-Kpong (1970 to 1982) and post- Kpong (1983-2018) dam to examine the impacts of dam regulation during different periods. Meanwhile, available Landsat remote sensing images of VRD were obtained from USGS from 1972 to 2018 to conduct the analysis of morphological evolution. The two separate remote sensing images that cover the VRD, that is, path 193, row 56 and path193, row 56 were merged using the mosaicking toolbox in ENVI classic software. The shoreline was extracted manually in ArcGIS 10.3 using 432 bands and 543 bands pseudo-colour image for MSS and TM/ETM images, respectively. Delta area was further calculated after the extraction of the shoreline. The accretion-erosion rates were calculated and their relationship with the cumulative sediment load were also analyzed. The average river discharge and sediment load for the pre-dam period were 1237 m3/s and 5.9×105 m3/d with a standard variation of 516.8 m3/s and 2.48 ×105 m3/d, respectively, whereas those for the post-dam period were 949 m3/s and 4.6×104 m3/d with a standard variation of 196.1 m3/s and 0.94×104 m3/d, respectively. The decreasing rates of river discharge and sediment load were 23.23% and 92.3%, respectively. The nonuniformity coefficients of river discharge were 1.45, 0.07 and 0.09 for the periods of pre-Akosombo, pre- Kpong dam and post- Kpong dam, respectively. Whereas the regulated coefficients of river discharge for those periods were 0.55, 0.03 and 0.04, respectively. The nonuniformity coefficients of sediment load were 1.44, 0.04 and 0.09 for the periods of pre-Akosombo, pre- Kpong dam and post- Kpong dam, respectively. Whereas the regulated coefficients of sediment load for those periods were 0.55, 0.03 and 0.04, respectively. The results show that the intra-annual and inter-annual variations are higher in the pre-dam construction period than the post-dam construction period. The construction of the Akosombo dam affects the intra-annual variation of river discharge more significantly than the Kpong dam. As against earlier reports of continuous erosion of the shoreline in previous studies, this study suggested that a more stable shoreline exists in the VRD with small fluctuations of erosion or accretion less than 0.56%. The relationship between cumulative sediment load and the changes of the delta area is weak, which suggest the variation of the sediment load have little effect on the evolution of the delta area of the modern VRD. As a result, VRD underwent severe erosion before the 1970s due to the reduction of the sediment, however, the VRD has achieved an equilibrium state since 1970s. The VRD could stay in the equilibrium state as the sediment load is kept at the current level. This study investigates the effects of dam regulation on the hydrological alteration and morphological evolution of the VRD, which provides support for the future regulation of the Volta River and the restoration of the Volta River Delta. At the same time, the results provide scientific insights for the future evolution of similar deltas influenced by dam regulation, such as the Yellow River Delta (YRD) in China. As there is a continuous decrease of the sediment load of the Yellow River, its delta may be subjected to erosion first and then achieve an equilibrium state.