長(zhǎng)江上游水電開(kāi)發(fā)對(duì)流域生態(tài)環(huán)境影響初探
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1、 長(zhǎng)江上游水電開(kāi)發(fā)對(duì)流域生態(tài)環(huán)境影響初探*基金項(xiàng)目:水利部現(xiàn)代水利科技創(chuàng)新項(xiàng)目專(zhuān)題(XDS2004-02-3)資助; 作者簡(jiǎn)介:陳 進(jìn)(1959~ ),男,湖北武漢人,博士,教授級(jí)高工,主要從事流域水資源研究。 陳 進(jìn)1 翁立達(dá)2 1長(zhǎng)江水利委員會(huì)長(zhǎng)江科學(xué)院,武漢,430010 2長(zhǎng)江水利委員會(huì)長(zhǎng)江流域水資源保護(hù)局,武漢,430010 摘 要 長(zhǎng)江水能資源豐富,其中上游地區(qū)水能蘊(yùn)藏量占全流域近90%,未來(lái)20年,長(zhǎng)江上游地區(qū)將有一大批水電工程開(kāi)工建設(shè),屆時(shí)在長(zhǎng)江上游干支流將形成較大規(guī)模的梯級(jí)水電站群,這些水電站及水庫(kù)投入運(yùn)行
2、后,將對(duì)長(zhǎng)江上游及全流域的生態(tài)與環(huán)境產(chǎn)生重要影響。本文根據(jù)已有規(guī)劃成果,預(yù)測(cè)未來(lái)長(zhǎng)江上游梯級(jí)水電工程的格局;討論上游地區(qū)生態(tài)與環(huán)境對(duì)水電站建設(shè)的制約因素;初步分析梯級(jí)水庫(kù)群對(duì)于長(zhǎng)江水生生物,特別是魚(yú)類(lèi)的影響;最后提出減緩梯級(jí)水庫(kù)群對(duì)流域生態(tài)與環(huán)境影響的對(duì)策。 關(guān)鍵詞 長(zhǎng)江上游,水電站,梯級(jí)水庫(kù),生態(tài)與環(huán)境,洄游性魚(yú)類(lèi) 1 前 言 長(zhǎng)江水量豐富,水流落差大,水能資源豐富,根據(jù)近期普查成果,全流域水能資源理論蘊(yùn)藏量平均功率27781億kW,年發(fā)電量24336億kWh,約占全國(guó)總量的40%,其中技術(shù)可開(kāi)發(fā)量25627億kW,年發(fā)電量11879億kWh,約占全國(guó)總量的48%,經(jīng)濟(jì)可開(kāi)發(fā)
3、量22832億kW,年發(fā)電量10498億kWh,約占全國(guó)總量的60%。長(zhǎng)江流域水能資源的89.4%集中在上游地區(qū)。開(kāi)發(fā)可再生的水能資源對(duì)于我國(guó)能源發(fā)展戰(zhàn)略無(wú)疑具有重要意義,但大規(guī)模的梯級(jí)水庫(kù)的建設(shè)和運(yùn)行將顯著改變長(zhǎng)江天然的水文過(guò)程、水沙分配比例,生境的改變將對(duì)流域生態(tài)系統(tǒng)與環(huán)境產(chǎn)生重大影響。如果規(guī)劃的水電工程全部實(shí)施,長(zhǎng)江上中游干流和相當(dāng)多的支流將被部分渠化或完全渠化,自然河流將轉(zhuǎn)變?yōu)榘胩烊缓恿骰蛉斯た刂频暮恿?,這種變化將給長(zhǎng)江的生態(tài)系統(tǒng)和環(huán)境帶來(lái)長(zhǎng)期的影響。健康的長(zhǎng)江不僅應(yīng)該為人類(lèi)服務(wù),而且也應(yīng)為流域自然生態(tài)系統(tǒng)提供良好的環(huán)境,流域水文循環(huán)和生態(tài)系統(tǒng)的維持需要自然的長(zhǎng)江。所以,在開(kāi)發(fā)和利用長(zhǎng)
4、江的水能時(shí),應(yīng)該充分認(rèn)識(shí)到長(zhǎng)江本來(lái)是水文循環(huán)的產(chǎn)物,水文循環(huán)的基本特征是水流的連通性、動(dòng)態(tài)性、可循環(huán)性,應(yīng)該維持自然的水文循環(huán)。本文針對(duì)長(zhǎng)江上游水電開(kāi)發(fā)現(xiàn)狀及未來(lái)水電規(guī)劃,分析長(zhǎng)江上游地區(qū)未來(lái)水電站的格局;討論梯級(jí)水庫(kù)建設(shè)對(duì)水沙過(guò)程等環(huán)境因素引起的變化;探討這種變化對(duì)長(zhǎng)江自然生境的影響,以魚(yú)類(lèi)為典型水生生物,討論梯級(jí)水庫(kù)群對(duì)生態(tài)與環(huán)境的影響方式和問(wèn)題;最后提出減小水電工程對(duì)生態(tài)與環(huán)境影響的對(duì)策。 2 長(zhǎng)江的水電站及水庫(kù)建設(shè) 長(zhǎng)江流域第一座水電站——石龍壩建于1910年,到1949年全流域共建成31座水電站,全是小水電,總裝機(jī)容量?jī)H13.4MW。解放后,水電站及水庫(kù)建設(shè)發(fā)展迅速,50-60
5、年代,水電開(kāi)發(fā)主要集中在交通便利和經(jīng)濟(jì)相對(duì)發(fā)達(dá)的中下游地區(qū),60年代到80年代,上、中、下游地區(qū)水電建設(shè)全面展開(kāi),到20世紀(jì)后期至本世紀(jì),為適應(yīng)西部大開(kāi)發(fā)戰(zhàn)略和“西電東送”要求,我國(guó)水電開(kāi)發(fā)的重點(diǎn)轉(zhuǎn)移到水能資源豐富的長(zhǎng)江上游和西南諸河等地區(qū),到2001年底,全流域已建和在建水電站2441座,裝機(jī)容量69727.1MW,年發(fā)電量2924.96億kWh,占全國(guó)水電裝機(jī)容量的70%左右。全流域已建、正建水電站裝機(jī)容量和年發(fā)電量分別占經(jīng)濟(jì)可開(kāi)發(fā)量的30.5%和27.9%。從地區(qū)分布來(lái)看,中下游地區(qū)水能開(kāi)發(fā)利用程度已經(jīng)超過(guò)50%,上游地區(qū)不到20%,而長(zhǎng)江江源至宜賓河段,水電開(kāi)發(fā)不到經(jīng)濟(jì)可開(kāi)發(fā)量的5%,
6、所以,今后20年,長(zhǎng)江水電開(kāi)發(fā)的主戰(zhàn)場(chǎng)在長(zhǎng)江上游地區(qū)。 從水庫(kù)建設(shè)規(guī)模來(lái)看,到2000年為止,長(zhǎng)江流域已經(jīng)建設(shè)水庫(kù)4.4萬(wàn)座,總庫(kù)容1373.37億m3,其中大型水庫(kù)109座,總庫(kù)容667.42億m3,中型水庫(kù)997座,總庫(kù)容242.00億m3,如果加上在建的大中型水庫(kù),總庫(kù)容超過(guò)2113億m3。表1給出了長(zhǎng)江上游地區(qū)主要干支流上規(guī)劃和建設(shè)的大中型水電站水庫(kù)庫(kù)容統(tǒng)計(jì)情況,從已建和在建水庫(kù)來(lái)看,烏江流域和上游干流區(qū)間河段水電開(kāi)發(fā)程度比較高,而其他流域水電開(kāi)發(fā)程度還比較低,但各河段規(guī)劃的水庫(kù)較多,特別是金沙江流域規(guī)劃的水庫(kù)總庫(kù)容將達(dá)到徑流量的83%。隨著規(guī)劃水電站的逐步實(shí)施,長(zhǎng)江上游地區(qū)水庫(kù)總庫(kù)
7、容將達(dá)到河川徑流量的61%,如果考慮大量的小型水庫(kù)和塘庫(kù),水庫(kù)控制的地表徑流量將超過(guò)年徑流量的70%以上,除赤水河等少數(shù)支流外,長(zhǎng)江上游干流決大多數(shù)河段都將布滿梯級(jí)水庫(kù),相當(dāng)多的天然河流將轉(zhuǎn)為人工控制的河道。 表1 長(zhǎng)江上游大中型水庫(kù)建設(shè)情況(2001年為止) 流域 年徑流量(億m3) 已建水庫(kù)總庫(kù)容 (億m3) 在建水庫(kù)庫(kù)容 (億m3) 已建在建水庫(kù)庫(kù)容(億m3) 已建在建水庫(kù)占年徑流量的比例(%) 規(guī)劃水庫(kù)庫(kù)容 (總庫(kù)容) (億m3) 總庫(kù)容占年徑流量的比例(%) 金沙江 1565.2 0 0 0 0 1300(1
8、300) 83 岷沱江 1065.0 5.9 70.0 75.9 7 260(335.9) 32 嘉陵江 698.8 37.1 25.3 62.4 9 171.6(234.0) 33 烏江 551.1 30.5 166.0 196.5 36 73.5(270.0) 49 宜賓至 宜昌 634.8 42.9 479.6 522.6 82 83.3(605.9) 95 長(zhǎng)江上游合計(jì) 4514.9 116.4 740.9 857.4 19 1887.6(2745) 61 3 上游地區(qū)水電開(kāi)發(fā)的制約因素 長(zhǎng)江上游
9、流域面積約100萬(wàn)km2,不僅水能資源豐富,而且森林、礦產(chǎn)和旅游等資源也十分豐富,同時(shí),長(zhǎng)江上游區(qū)處于我國(guó)地形第一和第二階梯,地勢(shì)陡峻,山高谷深,土層淺薄,地質(zhì)構(gòu)造活動(dòng)強(qiáng)烈,外動(dòng)力地質(zhì)現(xiàn)象如泥石流、滑坡、山崩等災(zāi)害嚴(yán)重,生態(tài)與環(huán)境脆弱。 長(zhǎng)江上游地區(qū)森林資源十分豐富,是我國(guó)僅次于東北的第二大林區(qū),也是長(zhǎng)江水土資源保護(hù)的重要屏障。森林主要分布在金沙江、岷江、大渡河、嘉陵江等河流的上游。多年來(lái),由于不合理開(kāi)發(fā),重伐輕造,森林植被銳減。不少地區(qū)的森林已經(jīng)破壞,有些演替為草灌群落,生態(tài)系統(tǒng)自我調(diào)節(jié)能力大為下降,土地退化和水土流失面積不斷擴(kuò)大。 長(zhǎng)江上游地區(qū)礦產(chǎn)也十分豐富,銅、鉛、鋅、銻、鎢、鈷、錫
10、、鐵、錳、鋁等儲(chǔ)量,約占全國(guó)的30%-50%;鎂、釩、鈦、汞儲(chǔ)量占全國(guó)80%左右,磷礦幾乎全部在長(zhǎng)江流域,一塊占全國(guó)土地總面積0.7%的攀西地區(qū),就蘊(yùn)藏著占全國(guó)95%的鈦、54%的釩、20%的鐵。 長(zhǎng)江現(xiàn)有魚(yú)類(lèi)370種,分別屬于17目、52科、178屬,其中純淡水魚(yú)類(lèi)294種,咸淡水魚(yú)類(lèi)22種,海淡水回游魚(yú)類(lèi)9種,海水魚(yú)類(lèi)45種。上游地區(qū)的魚(yú)類(lèi)種類(lèi)繁多,共有魚(yú)類(lèi)230種,其中僅見(jiàn)于上游水體的有103種,如中華腹裂魚(yú)、重口腹裂魚(yú)、布氏哲羅魚(yú)等受到特殊的自然條件影響,僅在上游地區(qū)形成優(yōu)勢(shì)種群。 長(zhǎng)江上游地區(qū)是水系、山脈、生物和人文的綜合體,風(fēng)景名勝和人文古跡眾多,具有自然遺產(chǎn)、觀賞和科學(xué)研究等
11、價(jià)值。如有三峽、九寨溝、黃果樹(shù)、三江并流等自然奇觀,有國(guó)寶大熊貓棲息地。到2003年為至,已經(jīng)建立國(guó)家級(jí)自然保護(hù)區(qū)32個(gè),保護(hù)區(qū)面積達(dá)到200萬(wàn)公頃。長(zhǎng)江上游每一條河流由于所處的地理位置不同,景色各異,自然風(fēng)光具有唯一性。長(zhǎng)江上游地區(qū)人類(lèi)活動(dòng)已經(jīng)有100萬(wàn)年的歷史,有各類(lèi)重要遺址數(shù)十處,文物點(diǎn)更是數(shù)不勝數(shù),僅受三峽水庫(kù)影響的文物點(diǎn)就達(dá)1087處。 所以,在進(jìn)行梯級(jí)水庫(kù)規(guī)劃和建設(shè)時(shí),特別是大型水庫(kù)建設(shè)時(shí),應(yīng)該深入了解上游地區(qū)生態(tài)與環(huán)境敏感點(diǎn),充分考慮所在河流生態(tài)、資源、環(huán)境和人文等方面的制約因素,避免或減少水電開(kāi)發(fā)對(duì)生態(tài)與環(huán)境的影響。 4 梯級(jí)水庫(kù)帶來(lái)生境的變化 生態(tài)系統(tǒng)包括非生物部分(
12、即生境)和生物部分,梯級(jí)水庫(kù)對(duì)生態(tài)與環(huán)境的影響首先體現(xiàn)在對(duì)生境的改變,包括河流水沙輸移過(guò)程、水體的連續(xù)性、流態(tài)、流速、水溫、溶解氧和透明度等環(huán)境要素的變化,主要影響在以下幾方面: (1)梯級(jí)水庫(kù)對(duì)河流最直接的影響是破壞了河流的連續(xù)性。長(zhǎng)江上游是許多洄游魚(yú)類(lèi)的重要棲息地,洄游魚(yú)類(lèi)需要三場(chǎng)一道(繁殖場(chǎng),育肥場(chǎng)、產(chǎn)卵場(chǎng),洄游通道),梯級(jí)水庫(kù)的建設(shè)造成洄游魚(yú)類(lèi)等水生生物的生命通道阻隔,相當(dāng)多的洄游魚(yú)類(lèi)可能滅絕。由于修建魚(yú)道不僅增加工程成本和技術(shù)難度,而且較難評(píng)價(jià)其效果,所以目前已建和在建大壩基本上沒(méi)有考慮修建魚(yú)道。徑流式電站雖然河流水文過(guò)程影響較小,但水流利用率一般很高,河道水流基本上通過(guò)引水管道和
13、水輪機(jī)流過(guò),也會(huì)對(duì)魚(yú)類(lèi)等水生生物帶來(lái)毀滅性打擊。例如,岷江上游建設(shè)了大量引水式水電站,雖然沒(méi)有建高壩大庫(kù),但造成相當(dāng)長(zhǎng)的河段,在枯季完全脫流,全部河水都從壓力管道流過(guò),對(duì)洄游魚(yú)類(lèi)等水生生物有致命打擊,如珍稀魚(yú)類(lèi)-虎嘉魚(yú)已經(jīng)基本消失。洄游魚(yú)類(lèi)是水生態(tài)系統(tǒng)中關(guān)鍵生物指標(biāo)物種之一,它的滅亡將影響整個(gè)河流生態(tài)系統(tǒng)的結(jié)構(gòu)和生態(tài)系統(tǒng)的完整性。 (2)大中型水庫(kù)的人工調(diào)節(jié)雖然顯著提高了人類(lèi)利用水的保證率,但同時(shí)也使自然河道的洪枯過(guò)程減弱,甚至消失。而相當(dāng)多的水生生物需要河流的洪枯變化。洪水是自然現(xiàn)象,河流和河道的形成需要洪水,沒(méi)有洪水,就沒(méi)有河流,河道就會(huì)萎縮,河流的生態(tài)功能就會(huì)下降。洪枯變化帶來(lái)了河流水
14、位、水溫、水量、含沙量和消落帶等的變化,生物多樣性常常與生境的復(fù)雜性直接相關(guān),這些現(xiàn)象是河流生境的體現(xiàn),是生物多樣性需要的自然環(huán)境。當(dāng)然,特大洪水對(duì)人類(lèi)和自然生態(tài)都有巨大的破壞,但一般性洪水卻是自然生態(tài)所需要的,許多水生生物和兩棲生物需要在河灘上產(chǎn)卵,如果河水常年不上灘,生物棲息地將大為減少。研究表明,降雨與徑流的依時(shí)變化是河流和濕地的植物、無(wú)脊椎動(dòng)物和魚(yú)類(lèi)生命循環(huán)的主要驅(qū)動(dòng)力,季節(jié)性高峰流量的喪失會(huì)導(dǎo)致魚(yú)類(lèi)產(chǎn)卵、孵化和遷徙激發(fā)因素的中斷,一些魚(yú)類(lèi)遇洪水或急流才能刺激產(chǎn)卵和幼苗生長(zhǎng)。河流洪水過(guò)程的減弱,使魚(yú)類(lèi)較難進(jìn)入濕地或回水區(qū),改變了水生生物的食物網(wǎng)結(jié)構(gòu),岸邊植被復(fù)原能力降低或消失,植被生長(zhǎng)
15、的速度減緩。 (3)大水庫(kù)的建設(shè)對(duì)庫(kù)區(qū)生境影響巨大。庫(kù)區(qū)水流速度減小,水體納污能力和自凈能力下降,特別是在水庫(kù)支汊區(qū)域,水體污染物很難擴(kuò)散。水庫(kù)淹沒(méi)大量灘地,魚(yú)類(lèi)和兩棲動(dòng)物的棲息地減少。水庫(kù)水體深度較大,水溫會(huì)產(chǎn)生分層,水庫(kù)下泄的低溫水對(duì)下游水生生物和農(nóng)田灌溉都會(huì)產(chǎn)生不利影響。泥沙淤積將影響水庫(kù)的使用壽命,庫(kù)尾淤積將影響回水變動(dòng)區(qū)航運(yùn)和碼頭。 (4)梯級(jí)水庫(kù)的建設(shè)和運(yùn)行將在相當(dāng)長(zhǎng)的時(shí)間內(nèi)使中下游河道輸沙量和水體的含沙量減少。正常的河流需要平衡輸沙,河岸穩(wěn)定、河口演變、營(yíng)養(yǎng)物的輸送、水體凈化和生態(tài)維持都需要一定的輸沙。例如,三峽水庫(kù)的清水下泄,長(zhǎng)江中下游河段將發(fā)生長(zhǎng)時(shí)間的沖刷,河床下降,沿岸
16、地下水位也會(huì)下降,使河勢(shì)變化和沿岸濕地生境受到影響。在平原湖區(qū),由于長(zhǎng)江水位下降,進(jìn)入洞庭湖的洪水會(huì)減少,洞庭湖會(huì)加速退化,江湖關(guān)系將發(fā)生變化。清水下泄,對(duì)河岸會(huì)產(chǎn)生侵蝕,江水對(duì)周邊濕地下水交換將減少,同時(shí)可能對(duì)兩岸堤防安全構(gòu)成威脅。長(zhǎng)江河口地區(qū)由于長(zhǎng)期缺乏泥沙的補(bǔ)給,岸線將受海潮的侵蝕,河口自然演變規(guī)律和生境發(fā)生變化,同時(shí)對(duì)河口岸線利用也將產(chǎn)生不利影響。尼羅河三角洲在阿斯旺水庫(kù)修建后,進(jìn)入河口的泥沙減少,導(dǎo)致海岸線不斷后退和侵蝕。因此,河流的沙多了不好,沙少了也不行,應(yīng)該重視水體含沙量減少帶來(lái)的新問(wèn)題。 (5)大規(guī)模的水庫(kù)建設(shè)對(duì)區(qū)域氣候、水文循環(huán)和環(huán)境變化有一定影響。水庫(kù)的建設(shè),將增加水的
17、蒸發(fā)和滲漏損失,使下泄徑流量減小,如漢江流域,丹江口水庫(kù)建設(shè)后,90年代以來(lái)上游來(lái)水量減少了10%以上,原因有區(qū)域氣候變化的影響,也有水庫(kù)蒸發(fā)和滲漏的影響。再如,阿斯旺水庫(kù)每年蒸發(fā)和滲漏損失水量達(dá)210億m3,達(dá)到水庫(kù)總庫(kù)容的10%以上。隨著長(zhǎng)江上游大規(guī)模的水電站建設(shè),已經(jīng)開(kāi)始擔(dān)心水庫(kù)蓄不滿水的問(wèn)題。因?yàn)殚L(zhǎng)江雖然水資源豐富,但大部分是洪水,非汛期水量并不多,而大部分水庫(kù)都是汛后開(kāi)始蓄水,將加劇枯季人類(lèi)用水和生態(tài)用水的矛盾。另一方面,水庫(kù)的建設(shè),淹沒(méi)大量土地,移民搬遷將改變庫(kù)區(qū)土地利用方式,地下水位抬高,氣溫及氣候?qū)?huì)產(chǎn)生變化,區(qū)域水文循環(huán)和生境也將發(fā)生改變。另外,水庫(kù)還可能誘發(fā)地震、滑坡等地質(zhì)
18、災(zāi)害。 5 梯級(jí)水庫(kù)對(duì)生物的影響 梯級(jí)水庫(kù)對(duì)生物的影響是一個(gè)長(zhǎng)期和復(fù)雜的過(guò)程,自然生境的破壞,人工環(huán)境的產(chǎn)生,一些生物會(huì)通過(guò)自身的調(diào)整逐步適應(yīng)新的環(huán)境,繼續(xù)生存和發(fā)展,而另外一些生物會(huì)不適應(yīng)新的環(huán)境而出現(xiàn)物種退化或消亡。生態(tài)系統(tǒng)中任何生物的存在都有其特定的地位和作用,不同生物之間相互依存,一個(gè)生物的消亡,必然影響其它生物的存亡和整個(gè)生態(tài)系統(tǒng)的完整性。所以,大壩及水庫(kù)對(duì)生物的影響及生物對(duì)水庫(kù)建設(shè)的響應(yīng)是一個(gè)十分復(fù)雜的過(guò)程,需要長(zhǎng)期觀測(cè)和研究才會(huì)有定量的成果,這里以魚(yú)類(lèi)為例,說(shuō)明生物受水庫(kù)影響的情況。 長(zhǎng)江水系有浮游植物321種,常見(jiàn)的近330種,浮游動(dòng)物330種,常見(jiàn)種類(lèi)130種,底棲動(dòng)
19、物220種,水生高等植物214種,水生大型動(dòng)物中除魚(yú)類(lèi)外還有獸類(lèi)白鱀豚、江豚、爬行類(lèi)揚(yáng)子鱷和兩棲類(lèi)大鯇等珍惜物種,其中國(guó)家一級(jí)保護(hù)動(dòng)物白鱀豚、中華鱘、長(zhǎng)江鱘、白鱘;國(guó)家二級(jí)保護(hù)動(dòng)物江豚、胭脂魚(yú)、川陜哲羅鮭、秦嶺細(xì)鱗鮭、松江鱸魚(yú)等。梯級(jí)水庫(kù)對(duì)魚(yú)類(lèi)影響可以從以下幾方面來(lái)說(shuō)明: (1)隨著長(zhǎng)江干流葛洲壩和三峽水電站的建設(shè)和沿江大規(guī)模筑堤建閘工程,河海間洄游的魚(yú)類(lèi)如鱘魚(yú)、鰣魚(yú)等珍稀魚(yú)類(lèi)已大為減少。國(guó)家一級(jí)保護(hù)動(dòng)物中華鱘原產(chǎn)卵地原在長(zhǎng)江上游合江至屏山河段,長(zhǎng)約800km,原有16處產(chǎn)卵場(chǎng),葛洲壩電站建成后,雖然在壩下建立了人工產(chǎn)卵場(chǎng),但僅局限在5km范圍內(nèi),產(chǎn)卵場(chǎng)面積僅為原來(lái)的1-2%。國(guó)家一級(jí)保護(hù)動(dòng)
20、物白鱘產(chǎn)卵場(chǎng)分布于金沙江下游和重慶以上的長(zhǎng)江干流,產(chǎn)卵季節(jié)為3月-5月,習(xí)慣在河灘礫石間產(chǎn)卵。國(guó)家二級(jí)保護(hù)動(dòng)物胭脂魚(yú)產(chǎn)卵場(chǎng)在長(zhǎng)江上游岷江和嘉陵江等支流,魚(yú)卵具有微粘性、散布在石塊縫隙中發(fā)育,幼魚(yú)可隨江飄流到中下游及通江湖泊。如果在這些河段建設(shè)水庫(kù),河灘將淹沒(méi),必將影響到這些珍稀魚(yú)類(lèi)棲息地和洄游通道。 (2)長(zhǎng)江上游河段特有魚(yú)類(lèi),大多數(shù)終生在流水中生活,它們的形態(tài)結(jié)構(gòu)、生理特征和生態(tài)習(xí)性同棲息地的水流、河床物質(zhì)和底棲生物相適應(yīng),如巖原鯉、圓口銅魚(yú)等喜棲息于快速流淌、與大氣接觸面大,含氧量較高的水體,形成水庫(kù)后,在靜水中則會(huì)因溶解氧不足而死亡。 (3)長(zhǎng)江上主要的經(jīng)濟(jì)魚(yú)類(lèi)--四大家魚(yú)的產(chǎn)卵很大
21、程度上取決于水溫和漲水等環(huán)境因素,在四月底至五月初的繁殖期,如果水溫未達(dá)到18℃,即使?jié)q水也不產(chǎn)卵,如達(dá)到合適水溫,又遇降雨引起河流水位陡漲,可刺激家魚(yú)產(chǎn)卵,產(chǎn)卵規(guī)模和漲水幅度表現(xiàn)出正相關(guān),魚(yú)卵在隨水飄流過(guò)程中發(fā)育、孵化,飄流距離可達(dá)300-400km,且要求流速在0.2m/s以上,否則魚(yú)卵和魚(yú)苗會(huì)下沉而不能正常發(fā)育,像這樣魚(yú)卵飄流性的魚(yú)類(lèi),在長(zhǎng)江干流有20多種。在水庫(kù)內(nèi),因庫(kù)區(qū)河灘淹沒(méi),產(chǎn)卵場(chǎng)減少,魚(yú)卵也難以飄流孵化。 (4)長(zhǎng)江上游梯級(jí)水電站中,大部分是低水頭的徑流式電站,雖不是高壩大庫(kù),但水流利用率很高,90%以上的水流流經(jīng)水電站水輪機(jī)或壓力管道,魚(yú)類(lèi)等水生生物難以存活。而且徑流式水電
22、站絕大多數(shù)是日調(diào)節(jié)或無(wú)調(diào)節(jié)能力河道每日都有斷流時(shí)段,魚(yú)類(lèi)無(wú)法生存。另一方面,許多高壩大庫(kù)下泄水流,通過(guò)摻氣進(jìn)行消能防沖,保護(hù)河道,但同時(shí)造成水庫(kù)下游相當(dāng)長(zhǎng)的河段(可達(dá)數(shù)百公里)的河水氣體過(guò)飽和,幼魚(yú)吞食而造成氣泡病大量死亡。 6 對(duì) 策 長(zhǎng)江上游梯級(jí)水電站建設(shè)對(duì)流域生態(tài)與環(huán)境的影響十分復(fù)雜,短時(shí)間內(nèi)較難看出明顯影響,應(yīng)本著科學(xué)務(wù)實(shí)的態(tài)度全面客觀分析,處理好保護(hù)生態(tài)環(huán)境與水電開(kāi)發(fā)的關(guān)系。水電開(kāi)發(fā)的規(guī)劃、設(shè)計(jì)、建設(shè)和管理者應(yīng)該廣泛聽(tīng)取各方面的意見(jiàn),鼓勵(lì)公眾參與,盡量采取措施,減小水電工程對(duì)流域生態(tài)與環(huán)境的影響,建議采用的措施有: (1)政府及各部門(mén)、流域管理者、水庫(kù)管理者和利益相關(guān)者都應(yīng)
23、該具有生態(tài)與環(huán)境保護(hù)的理念,充分認(rèn)識(shí)到水電站建設(shè)和運(yùn)行給生態(tài)與環(huán)境帶來(lái)的不利用影響,同時(shí)應(yīng)該認(rèn)識(shí)到問(wèn)題的復(fù)雜性和長(zhǎng)期性。 (2)加強(qiáng)流域統(tǒng)一管理,在長(zhǎng)江干支流水資源綜合規(guī)劃中,應(yīng)從長(zhǎng)江全流域角度,根據(jù)各河段特點(diǎn),制定河流生態(tài)基流標(biāo)準(zhǔn),作為水電站規(guī)劃、設(shè)計(jì)、建設(shè)和運(yùn)行的依據(jù)。水電站建設(shè)必須保持河流必要的生態(tài)基流,并從流域的角度考慮梯級(jí)水電站的生態(tài)調(diào)度。 (3)以流域?yàn)閱卧?,定期進(jìn)行生態(tài)與環(huán)境監(jiān)測(cè),進(jìn)行長(zhǎng)期的科學(xué)觀測(cè)和科學(xué)研究,對(duì)水庫(kù)建設(shè)不僅應(yīng)進(jìn)行環(huán)境影響預(yù)測(cè)評(píng)價(jià),更重要的是需要建立后評(píng)估制度,在工程完成后觀測(cè)和分析對(duì)流域生態(tài)與環(huán)境的影響。 (4)水電站的規(guī)劃不能僅考慮水能利用的經(jīng)濟(jì)指標(biāo),還
24、要考慮水電站及水庫(kù)對(duì)各類(lèi)自然保護(hù)區(qū)及生態(tài)與環(huán)境敏感區(qū)的影響,應(yīng)將避免和減少這種影響作為規(guī)劃的重要目標(biāo)。對(duì)于已經(jīng)造成影響的,應(yīng)該采取必要的工程和非工程措施進(jìn)行修復(fù)。 (5)從法律等制度上建立合理的生態(tài)補(bǔ)償機(jī)制,需要水電站受益者向受影響的河流生態(tài)和弱勢(shì)群體進(jìn)行補(bǔ)償,建立流域生態(tài)與環(huán)境保護(hù)工作和研究費(fèi)用的投入機(jī)制。 參 考 文 獻(xiàn) [1] 長(zhǎng)江水利委員會(huì),長(zhǎng)江流域地圖集,北京:中國(guó)地圖出版社,1998年。 [2] 陶思明,濕地生態(tài)育保護(hù)。北京:中國(guó)環(huán)境科學(xué)出版社,2003年。 [3] 水力水電規(guī)劃設(shè)計(jì)總院,中國(guó)大中型水電站規(guī)劃圖集,1994年。 [4] 長(zhǎng)江水利委員會(huì),中國(guó)水力
25、資源復(fù)查成果,長(zhǎng)江流域-概述,2004年。 [5] 范繼輝,程根偉,張艷等,岷江上游水電梯級(jí)開(kāi)發(fā)存在的問(wèn)題及建議,中國(guó)水利,2005年第10期,47-49。 聯(lián)系地址:武漢市黃浦大街23號(hào),430010,長(zhǎng)江科學(xué)院 Email:chenjin12342003@ or cjcjcj@ 電話:027-82829755,13607178977 A Preliminary Approach on Impacts of Hydropower Development in Upper Yangtze River on Ecological Environment
26、Jin Chen1 Lida Weng2 1Changjiang River Scientific Research Institute of Changjiang Water Resources Commission, Wuhan, 430010, Email:chenjin12342003@ 2Yangtze River Valley Water Resources Protection Bureau of Changjiang Water Resources Commission, Wuhan, 430010, Email: wengld@
27、 Abstract There are abundant hydro-energy resources in the Yangtze River (also called Changjiang River), and the hydro-energy reserves in the upper reaches occupy nearly 90% of the whole valley. In future 20 years, a great amount of hydroelectric projects will be constructed in the upper reaches o
28、f Yangtze River, and a large scale of cascade hydropower stations will be formed in the main channel and branches in the upper reaches at that time. After construction and operation of these power stations and reservoirs, some important impacts will be produced on the ecology and environment in the
29、upper areas and even the whole valley. In the paper, distribution of cascade power stations in the upper reaches is forecasted according to completed plans; some restricting factors of ecology and environment on hydropower station constructions in upstream are discussed; the impacts of cascade reser
30、voirs on the habitat and Aquatic Life (such as fishes) in the valley ecosystem are discussed; and finally, some countermeasures for mitigating the impacts arisen from the cascade reservoirs are put forward. Introduction The Yangtze River is rich in water resource, big in water head and abundant
31、in hydropower resources. According to recent general investigation, for the theoretical reserves of hydropower in the whole valley, the average power is 27781×108kW, and annual electricity output is 24336×108kWh, accounting for about 40% of the total China; 90% of the hydropower resources in the Yan
32、gtze River are distributed in upper areas. Undoubtedly, the development of renewable hydropower resources has vital significance for energy development strategy of China, but the construction and operation of large scale reservoirs will make the flow process, water-sediment proportion and ecosystem
33、 habitat change greatly, and the change of habitat will affect the natural ecosystem and environment significantly. If the planned hydroelectric projects are carried out completely, the main stems and quite a few branches of the upper and middle Yangtze River will be channelized partially or complet
34、ely and the natural rivers will be transformed into semi-natural or artificial controlling rivers, which will result in long-term impacts on natural ecosystem and environment of Yangtze River. Healthy Yangtze River should not only serve the human beings, but also provide good environment for the nat
35、ural ecosystem of valley, and the natural hydrologic cycle and ecosystem maintenance also need the Yangtze River. Therefore, in the development and utilization of hydropower, it should be fully realized that the Yangtze River is originally the product of hydrologic cycle, it need participate in and
36、maintain the natural hydrologic cycle; the basic features of river hydrologic cycle include connectivity, flow dynamic characteristics and periodicity. In the paper, in view of the present situations and the plan of future hydropower stations in the upper Yangtze River, the layout of cascade power s
37、tations of the upper reaches is analyzed; the changes of environmental factors such as water and sediment process etc. produced by the construction of cascade reservoirs are discussed; the impacts on aquatic life, such as fish ,since habitat changes are discussed; and finally, the countermeasures fo
38、r mitigating the impacts arisen from cascade reservoirs are proposed. Construction of Hydropower Stations and Reservoirs in the Yangtze River Shilong Dam, the first hydropower station in the Yangtze River Basin was built in 1910; and up to 1949, 31 dams had been built in the whole valley and all o
39、f them are of small ones, with the total installed capacity of 134mw. After 1949, hydropower stations and reservoirs were developed rapidly in 1950s ~1960s, and the hydropower development was located in the middle and lower areas with convenient traffic and developed economy; from 1960s to 1980s, th
40、e construction of hydropower stations in the upper, middle and lower reaches were in full swing; up to the late 20th century and the early 21st century, in order to meet the requirements of West Development strategies and “West-to-East Power Transmission”, the stress of hydropower development was tr
41、ansferred to the upper Yangtze and the rivers of Southwest China, and up to December of 2001, 2441 hydropower stations had been built or are under construction, with installed capacity of 69727.1mw, and annual electricity output of 2924.96×108 kWh, accounting for about 70% of the total installed hyd
42、ropower capacity in China. The installed capacity and annual electricity output of power stations having been built or under construction made up 30.5% and 27.9% of the economically developable reserves respectively. From the distribution in region, more than 50% of the hydropower in the middle and
43、lower Yangtze have been developed and utilized, while only less than 20% for the upper areas, and for the stretch from headwaters to Yibin, less than 5% of economically developable reserves have been utilized for hydropower development. Therefore, in the future 20 years, the hydropower development o
44、f the Yangtze River will be carried out mainly in the upper reaches. Viewed from reservoir construction, up to 2000, 44000 reservoirs had been constructed in the Yangtze River Basin with total storage capacity of 1373.37×108 m3, including 109 large-scale reservoirs with total storage capacity of 66
45、7.42×108 m3, 997 medium-sized reservoirs with total storage capacity of 242.00×108 m3, and the total storage capacity would exceed 2113×108 m3 inclusive of the large and medium scale reservoirs under construction. Table 1 shows the statistics of storage capacity of existing and planned large and med
46、ium reservoirs in main stems and branches of the upper Yangtze River, it can be seen that the degree of hydropower development in Wujiang River and main stems in upper Yangtze River is quite high, while it is lower in other valleys, but there are more reservoirs in planning for each reach, especiall
47、y in Jinsha River, the total storage capacity in planning will reach 83% of river runoff. With gradual implementation of the planning reservoirs, the total reservoirs storage capacity of upper Yangtze River will reach 61% of river runoff. If a large amount of small scale reservoirs are considered, t
48、he surface runoff controlled by reservoirs will exceed more than 70% of annual runoff; and except a few branches such as Chishui River, cascade reservoirs will be arranged in most of reaches in upper Yangtze River, and quite a few natural rivers will be transferred to artificially controlled river.
49、 Table 1 Large and Medium Scale Reservoirs in Upper Yangtze River (up to 2001) River Annual runoff(108m3) Storage capacity of existing reservoirs (108m3) Storage capacity of reservoirs under construction (108m3) Storage capacity of reservoir in planning (total storage capacity) (108m3) Pe
50、rcentage of total storage capacity to annual runoff (%) Jinsha River 1565.2 0 0 1300(1300) 83 Mintuo River 1065.0 5.9 70.0 260(335.9) 32 Jialing River 698.8 37.1 25.3 171.6(234.0) 33 Wujiang River 551.1 30.5 166.0 73.5(270.0) 49 Yibin to Yichang 634.8 42.9 479.6 83.3(605
51、.9) 95 Total of upper Yangtze River 4514.9 116.4 740.9 1887.6(2745) 61 Some restricting factors on hydropower development of Upper Yangtze River The upper Yangtze River Basin covers the area of 100×104 km2 approximately, with abundant hydropower resources, as well as forest, mineral and to
52、urist resources. In addition, it is located in the first and second topographic cascades of China, with steep terrain, high mountain and deep valley, shallow and thin soil layer, intense geological activity, serious external dynamic geologic disaster such as mud-rock flow, landslide, and landfall, a
53、nd frail ecology and environment. The upper Yangtze River, with extremely rich forest resources is the second forested area in China, next only to northeast China, and also an important barrier for water and soil conservation of the Yangtze River. The forest is mainly distributed in upper Yangtze R
54、iver such as Jinsha River, Minjiang River, Dadu River, and Jialing River and so on. However, the forest has reduced sharply due to unreasonable development, over-cutting and neglect of forestation for many years. Once the forest is destroyed, it is very difficult to restore, and as succession, grass
55、 & shrub degradation will occur quickly, the self-adjustment ability of ecosystem decreases greatly, and land degeneration area expands continuously. The mineral resources are also abundant in the upper Yangtze River, including copper, lead, zinc, stibium, tungsten, cobalt, tin, iron, manganese and
56、 aluminum, approximately making up 30%~50% of the total China; the reserves of magnesium, vanadium, titanium and mercury account for about 80% of the total China, and all phosphate rock distributes in the Yangtze River Basin nearly; only in Panxi, with the area accounting for 0.7% of the total area
57、in China, possesses titanium, vanadium and iron respectively accounting for 95%, 54% and 20% of the total China. In the Yangtze River, there are 370 kinds of fish belonging to 17 orders, 52 families and 178 genera separately, including 294 kinds of pure freshwater fish, 22 kinds of salt freshwater
58、fish, 9 kinds of sea freshwater migratory fish, and 45 kinds of marine fish. There are many kinds of fish in upper Yangtze River, totaling 230, 103 kinds are found only in upper reaches due to the influence of special natural conditions, and a dominant population is formed in upper reaches, such as
59、Chinese sschizothoracin, David’ sschizothoracin, Hucho bleekeri and so on. The upper Yangtze River is a synthesis of river system, mountain chain, biology and human culture, it possesses numerous sceneries and historic sites, and it is valuable in natural heritage, sightsee and scientific research,
60、 such as the natural marvelous spectacles like Three Gorges, Jiuzaigou, Huangguoshu, Three Parallel Rivers, the habitat of giant panda and other protected areas. Up to 2003, 32 national natural protected areas had been established, with the protected area of two million hm2, accounting for about 1/5
61、 of the upstream area. Each river of upper Yangtze River is different in landscape due to different geographic position; therefore, the natural scenery is unique. Long before one million years human activity has existed in the upper Yangtze. There are many important legacies and incalculable cultur
62、al relic spots. The cultural relic spots only influenced by the Three Gorges reservoir reach 1087. Therefore, When planning and construction of cascade reservoirs, especially the large-scale reservoirs, the sensitive points of ecology and environment should be thoroughly understood, the restricting
63、 factors of river ecology, resources, environment and human culture should be taken full consideration, and the impacts of hydropower development on ecology and environment should be avoided or mitigated. Changes of Habitat Caused by Cascade Reservoirs The ecosystem consists of abiotic factor (nam
64、ely habitat) and biotic factor, the impacts of cascade reservoirs on ecology and environment are represented by the change of habitat first, including water and sediment transportation process; river continuity, flow pattern, flow velocity, water temperature, dissolved oxygen and transparency of wat
65、er body, the main impacts involve following aspects: (1) The most direct impact of cascade reservoirs is that continuity of river is breached. The upper Yangtze River is an important habitat of many migratory fishes, and migratory fish need three fields and one pass (breeding field, fattening field
66、, spawning field, and migration pass). But the construction of cascade reservoirs will make the life channel of aquatic life(like migratory fish) obstruct, quite a few migratory fishes may become extinct. Up to now, no any consideration has been given to the ecological pass, such as fish-way, for the dams having been constructed and under construction because fish-way construction make the construction cost and technical difficulties increase, an
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